Bug 502004 - Losing Type-C/DP 4K@160Hz external monitor detection after reboot on ASUS Zenbook S 14 UX5406SA
Summary: Losing Type-C/DP 4K@160Hz external monitor detection after reboot on ASUS Zen...
Status: REPORTED
Alias: None
Product: systemsettings
Classification: Applications
Component: kcm_kscreen (show other bugs)
Version: 6.3.3
Platform: Other Linux
: NOR normal
Target Milestone: ---
Assignee: kscreen-bugs-null@kde.org
URL:
Keywords: multiscreen
Depends on:
Blocks:
 
Reported: 2025-03-26 01:23 UTC by Fangru Shao
Modified: 2025-04-12 04:39 UTC (History)
4 users (show)

See Also:
Latest Commit:
Version Fixed In:
Sentry Crash Report:


Attachments
External not showing in Display Configuration (289.33 KB, image/png)
2025-03-26 01:23 UTC, Fangru Shao
Details
External screen (Philips Consumer...) with Internal screen (259.10 KB, image/png)
2025-03-26 15:12 UTC, Fangru Shao
Details
Both laptop output and external monitor enabled (245.32 KB, image/png)
2025-03-26 21:29 UTC, Fangru Shao
Details
Some invisible display (257.02 KB, image/png)
2025-03-26 21:31 UTC, Fangru Shao
Details
With HDMI cable (4k@60Hz) (258.22 KB, image/png)
2025-03-27 03:35 UTC, Fangru Shao
Details

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Description Fangru Shao 2025-03-26 01:23:51 UTC
Created attachment 179740 [details]
External not showing in Display Configuration

I am using ASUS Zenbook S 14 UX5406SA.

While using Type-C to DP cable to connect to an 4K@160Hz external monitor, the monitor itself could first work normally but in KDE's System Settings - Display Configuration, the external monitor would not be there as shown in the attachment. Then usually after the reboot the system would not be able to detect the external monitor while keeping everything e.g. cable connection as same. The situation won't happen if I use HDMI to HDMI cable to only output 4K@60Hz or using the Type-C to DP cable to output 4K@160Hz in Windows so I could make sure the cable is okay.

Here is the graphic-part output of `inxi -Fazy`.

```
Graphics:
  Device-1: Intel Lunar Lake [Intel Arc Graphics 130V / 140V] vendor: ASUSTeK
    driver: xe v: kernel arch: Xe2 process: TSMC n3 (3nm) built: 2024+ ports:
    active: DP-1 off: eDP-1 empty: DP-2,HDMI-A-1 bus-ID: 00:02.0
    chip-ID: 8086:64a0 class-ID: 0300
  Device-2: Shinetech ASUS FHD webcam driver: hid-sensor-hub,usbhid,uvcvideo
    type: USB rev: 2.0 speed: 480 Mb/s lanes: 1 mode: 2.0 bus-ID: 3-5:4
    chip-ID: 3277:0059 class-ID: fe01 serial: <filter>
  Display: wayland server: X.org v: 1.21.1.16 with: Xwayland v: 24.1.6
    compositor: kwin_wayland driver: X: loaded: modesetting
    alternate: fbdev,intel,vesa dri: iris gpu: xe display-ID: 0
  Monitor-1: DP-1 model: Philips 27M2N5810 serial: <filter> built: 2024 res:
    mode: 3840x2160 hz: 160 scale: 200% (2) to: 1920x1080 dpi: 163 gamma: 1.2
    size: 597x336mm (23.5x13.23") diag: 685mm (27") ratio: 16:9 modes:
    max: 3840x2160 min: 720x400
  Monitor-2: eDP-1 model: Samsung 0x419d built: 2022 res: 2880x1800 dpi: 242
    gamma: 1.2 size: 302x189mm (11.89x7.44") diag: 356mm (14") ratio: 16:10
    modes: 2880x1800
  API: EGL v: 1.5 hw: drv: intel iris platforms: device: 0 drv: iris
    device: 1 drv: swrast gbm: drv: iris surfaceless: drv: iris wayland:
    drv: iris x11: drv: iris
  API: OpenGL v: 4.6 compat-v: 4.5 vendor: intel mesa v: 25.0.2-arch1.2
    glx-v: 1.4 direct-render: yes renderer: Mesa Intel Graphics (LNL)
    device-ID: 8086:64a0 memory: 15.05 GiB unified: yes display-ID: :1.0
  API: Vulkan v: 1.4.309 layers: 4 device: 0 type: integrated-gpu
    name: Intel Graphics (LNL) driver: N/A device-ID: 8086:64a0
    surfaces: xcb,xlib,wayland
  Info: Tools: api: clinfo, eglinfo, glxinfo, vulkaninfo
    de: kscreen-console,kscreen-doctor wl: wayland-info
    x11: xdpyinfo, xprop, xrandr
```

SOFTWARE/OS VERSIONS

Operating System: EndeavourOS 
KDE Plasma Version: 6.3.3
KDE Frameworks Version: 6.12.0
Qt Version: 6.8.2
Kernel Version: 6.13.7-arch1-1 (64-bit)
Graphics Platform: Wayland
Processors: 8 × Intel® Core™ Ultra 7 258V
Memory: 30.8 GiB of RAM
Graphics Processor: Intel® Graphics
Comment 1 Nate Graham 2025-03-26 15:04:12 UTC
If you click on where it says, "Philips Consumer Electronics Company 27..." do you see all the screens listed there?
Comment 2 Fangru Shao 2025-03-26 15:08:44 UTC
I could see the external screen name and the internal screen name if I click the box, but in the blank box above it would still only show the internal screen...
Comment 3 Fangru Shao 2025-03-26 15:12:50 UTC
Created attachment 179754 [details]
External screen (Philips Consumer...) with Internal screen

As shown in the attachment, hope it helps.
Comment 4 Nate Graham 2025-03-26 17:27:13 UTC
Thanks. That's quite strange.
Comment 5 Oliver Beard 2025-03-26 19:58:26 UTC
This is strange — the ScreenView and device combobox are fed via the same model. The delegates should be there. I am going to speculate something has gone crazy and they're positioned/sized incorrectly (i.e. the arrangement is visible or offscreen).

Can you please provide the output of the following command:

kscreen-console outputs
Comment 6 Fangru Shao 2025-03-26 21:03:18 UTC
Of course and here you are:

$ kscreen-console outputs
START: Requesting Config
Received config. Took 6 milliseconds
Screen:
        maxSize: QSize(64000, 64000)
        minSize: QSize(0, 0)
        currentSize: QSize(1920, 1080)

-----------------------------------------------------

Id:  1
Name:  "eDP-1"
Type:  "Panel (Laptop)"
Connected:  true
Enabled:  false
Priority:  0
Rotation:  KScreen::Output::None
Pos:  QPoint(1920,0)
MMSize:  QSize(302, 189)
FollowPreferredMode:  false
Size:  QSize(2880, 1800)
Scale:  2
Clones:  None
Mode:  "1"
Preferred Mode:  "1"
Preferred modes:  QList("1", "2")
Modes: 
         "1"    "2880x1800@120"   QSize(2880, 1800)   120
         "10"    "2560x1440@60"   QSize(2560, 1440)   59.961
         "11"    "1920x1080@60"   QSize(1920, 1080)   59.963
         "12"    "1600x900@60"   QSize(1600, 900)   59.946
         "13"    "1368x768@60"   QSize(1368, 768)   59.882
         "14"    "1280x720@60"   QSize(1280, 720)   59.855
         "2"    "2880x1800@60"   QSize(2880, 1800)   60.001
         "3"    "1600x1200@60"   QSize(1600, 1200)   59.869
         "4"    "1280x1024@60"   QSize(1280, 1024)   59.895
         "5"    "1024x768@60"   QSize(1024, 768)   59.92
         "6"    "2560x1600@60"   QSize(2560, 1600)   59.987
         "7"    "1920x1200@60"   QSize(1920, 1200)   59.885
         "8"    "1280x800@60"   QSize(1280, 800)   59.81
         "9"    "2880x1620@60"   QSize(2880, 1620)   59.96
EDID Info: 
        Device ID:  "xrandr-Samsung Display Corp."
        Name:  ""
        Vendor:  "Samsung Display Corp."
        Serial:  ""
        EISA ID:  "ATNA40CU09-0"
        Hash:  "3e73fdfcdfa17ab42adfcb8d7ef9499f"
        Width:  30
        Height:  19
        Gamma:  2.2
        Red:  QQuaternion(scalar:1, vector:(0.682617, 0.316406, 0))
        Green:  QQuaternion(scalar:1, vector:(0.245117, 0.713867, 0))
        Blue:  QQuaternion(scalar:1, vector:(0.139648, 0.0439453, 0))
        White:  QQuaternion(scalar:1, vector:(0.3125, 0.329102, 0))

-----------------------------------------------------

Id:  2
Name:  "DP-1"
Type:  "DisplayPort"
Connected:  true
Enabled:  true
Priority:  1
Rotation:  KScreen::Output::None
Pos:  QPoint(0,0)
MMSize:  QSize(597, 336)
FollowPreferredMode:  false
Size:  QSize(3840, 2160)
Scale:  2
Clones:  None
Mode:  "16"
Preferred Mode:  "15"
Preferred modes:  QList("15")
Modes: 
         "15"    "3840x2160@60"   QSize(3840, 2160)   60
         "16"    "3840x2160@160"   QSize(3840, 2160)   160
         "17"    "3840x2160@144"   QSize(3840, 2160)   144
         "18"    "3840x2160@120"   QSize(3840, 2160)   120
         "19"    "3840x2160@120"   QSize(3840, 2160)   119.88
         "20"    "3840x2160@60"   QSize(3840, 2160)   60
         "21"    "3840x2160@60"   QSize(3840, 2160)   59.94
         "22"    "3840x2160@30"   QSize(3840, 2160)   30
         "23"    "3840x2160@30"   QSize(3840, 2160)   29.97
         "24"    "2560x1440@120"   QSize(2560, 1440)   120
         "25"    "2560x1440@60"   QSize(2560, 1440)   60
         "26"    "1920x1080@120"   QSize(1920, 1080)   119.965
         "27"    "1920x1080@120"   QSize(1920, 1080)   120
         "28"    "1920x1080@120"   QSize(1920, 1080)   119.88
         "29"    "1920x1080@60"   QSize(1920, 1080)   60
         "30"    "1920x1080@60"   QSize(1920, 1080)   60
         "31"    "1920x1080@60"   QSize(1920, 1080)   59.94
         "32"    "1920x1080@50"   QSize(1920, 1080)   50
         "33"    "1680x1050@120"   QSize(1680, 1050)   119.946
         "34"    "1680x1050@60"   QSize(1680, 1050)   59.954
         "35"    "1600x900@60"   QSize(1600, 900)   60
         "36"    "1280x1024@75"   QSize(1280, 1024)   75.025
         "37"    "1280x1024@60"   QSize(1280, 1024)   60.02
         "38"    "1440x900@60"   QSize(1440, 900)   59.887
         "39"    "1152x864@75"   QSize(1152, 864)   75
         "40"    "1280x720@60"   QSize(1280, 720)   60
         "41"    "1280x720@60"   QSize(1280, 720)   59.94
         "42"    "1280x720@50"   QSize(1280, 720)   50
         "43"    "1024x768@75"   QSize(1024, 768)   75.029
         "44"    "1024x768@60"   QSize(1024, 768)   60.004
         "45"    "800x600@75"   QSize(800, 600)   75
         "46"    "800x600@60"   QSize(800, 600)   60.317
         "47"    "720x576@50"   QSize(720, 576)   50
         "48"    "720x480@60"   QSize(720, 480)   60
         "49"    "720x480@60"   QSize(720, 480)   59.94
         "50"    "640x480@75"   QSize(640, 480)   75
         "51"    "640x480@73"   QSize(640, 480)   72.809
         "52"    "640x480@67"   QSize(640, 480)   66.667
         "53"    "640x480@60"   QSize(640, 480)   60
         "54"    "640x480@60"   QSize(640, 480)   59.94
         "55"    "640x480@60"   QSize(640, 480)   59.94
         "56"    "720x400@70"   QSize(720, 400)   70.082
EDID Info: 
        Device ID:  "xrandr-Philips Consumer Electronics Company-27M2N5810-WDA2441002495"
        Name:  "27M2N5810"
        Vendor:  "Philips Consumer Electronics Company"
        Serial:  "WDA2441002495"
        EISA ID:  ""
        Hash:  "bad80af7aaabe80c1d2a4daaf22c86a6"
        Width:  60
        Height:  34
        Gamma:  2.2
        Red:  QQuaternion(scalar:1, vector:(0.681641, 0.308594, 0))
        Green:  QQuaternion(scalar:1, vector:(0.260742, 0.676758, 0))
        Blue:  QQuaternion(scalar:1, vector:(0.139648, 0.0507813, 0))
        White:  QQuaternion(scalar:1, vector:(0.313477, 0.329102, 0))
Comment 7 Oliver Beard 2025-03-26 21:16:43 UTC
With the laptop output disabled, I would expect to see the external display in the arrangement view.

The problem doesn't seem to be based on sizing then. It all looks normal.
Comment 8 Fangru Shao 2025-03-26 21:29:57 UTC
Created attachment 179765 [details]
Both laptop output and external monitor enabled

If I both enable the laptop output and the external monitor, there seems to be a strange empty part which should have been the display for the external monitor.
Comment 9 Fangru Shao 2025-03-26 21:31:25 UTC
Created attachment 179766 [details]
Some invisible display

When I drag the laptop display in the arrangement box it also seems to be meeting some invisible display there.
Comment 10 Oliver Beard 2025-03-27 02:38:36 UTC
(In reply to Fangru Shao from comment #9)
> When I drag the laptop display in the arrangement box it also seems to be meeting some invisible display there.

Positioning is handled by the backend, rather than in the UI. If you hover over this "invisible display", does the cursor change to a grab cursor?

Also, it would be useful to see any errors that are spat out to the console. You can do this by running:

kcmshell6 kcm_kscreen

in a terminal. The output of that might reveal some UI errors that are causing this.
Comment 11 Fangru Shao 2025-03-27 02:53:04 UTC
Sadly it won't. Only hovering over the laptop screen but not the invisible one could make the cursor to a grab cursor.
I use the command `kcmshell6 kcm_kscreen` to open the display configuration and then close it without saving any changes, and we do have some error information as below:

$ kcmshell6 kcm_kscreen
qrc:/qt/qml/org/kde/kirigami/dialogs/Dialog.qml:301: TypeError: Cannot read property 'height' of null
qrc:/qt/qml/org/kde/kirigami/dialogs/Dialog.qml:142: TypeError: Cannot read property 'height' of null
qrc:/qt/qml/org/kde/kirigami/dialogs/Dialog.qml:300: TypeError: Cannot read property 'width' of null
qrc:/qt/qml/org/kde/kirigami/dialogs/Dialog.qml:150: TypeError: Cannot read property 'width' of null
qrc:/qt/qml/org/kde/kirigami/dialogs/Dialog.qml:300: TypeError: Cannot read property 'width' of null
qrc:/qt/qml/org/kde/kirigami/dialogs/Dialog.qml:150: TypeError: Cannot read property 'width' of null
Comment 12 Fangru Shao 2025-03-27 03:35:44 UTC
Created attachment 179773 [details]
With HDMI cable (4k@60Hz)

Just after a reboot the system could not detect the external Philips screen anymore no matter how I reconnect the Type-C to DP cable. Here is the screenshot if I use HDMI to HDMI cable to enable it as 4k@60Hz and the command results are as below:

$ kscreen-console outputs
START: Requesting Config
Received config. Took 4 milliseconds
Screen:
        maxSize: QSize(64000, 64000)
        minSize: QSize(0, 0)
        currentSize: QSize(1920, 1080)

-----------------------------------------------------

Id:  1
Name:  "eDP-1"
Type:  "Panel (Laptop)"
Connected:  true
Enabled:  false
Priority:  0
Rotation:  KScreen::Output::None
Pos:  QPoint(1920,180)
MMSize:  QSize(302, 189)
FollowPreferredMode:  false
Size:  QSize(2880, 1800)
Scale:  2
Clones:  None
Mode:  "1"
Preferred Mode:  "1"
Preferred modes:  QList("1", "2")
Modes: 
         "1"    "2880x1800@120"   QSize(2880, 1800)   120
         "10"    "2560x1440@60"   QSize(2560, 1440)   59.961
         "11"    "1920x1080@60"   QSize(1920, 1080)   59.963
         "12"    "1600x900@60"   QSize(1600, 900)   59.946
         "13"    "1368x768@60"   QSize(1368, 768)   59.882
         "14"    "1280x720@60"   QSize(1280, 720)   59.855
         "2"    "2880x1800@60"   QSize(2880, 1800)   60.001
         "3"    "1600x1200@60"   QSize(1600, 1200)   59.869
         "4"    "1280x1024@60"   QSize(1280, 1024)   59.895
         "5"    "1024x768@60"   QSize(1024, 768)   59.92
         "6"    "2560x1600@60"   QSize(2560, 1600)   59.987
         "7"    "1920x1200@60"   QSize(1920, 1200)   59.885
         "8"    "1280x800@60"   QSize(1280, 800)   59.81
         "9"    "2880x1620@60"   QSize(2880, 1620)   59.96
EDID Info: 
        Device ID:  "xrandr-Samsung Display Corp."
        Name:  ""
        Vendor:  "Samsung Display Corp."
        Serial:  ""
        EISA ID:  "ATNA40CU09-0"
        Hash:  "3e73fdfcdfa17ab42adfcb8d7ef9499f"
        Width:  30
        Height:  19
        Gamma:  2.2
        Red:  QQuaternion(scalar:1, vector:(0.682617, 0.316406, 0))
        Green:  QQuaternion(scalar:1, vector:(0.245117, 0.713867, 0))
        Blue:  QQuaternion(scalar:1, vector:(0.139648, 0.0439453, 0))
        White:  QQuaternion(scalar:1, vector:(0.3125, 0.329102, 0))

-----------------------------------------------------

Id:  2
Name:  "HDMI-A-1"
Type:  "HDMI"
Connected:  true
Enabled:  true
Priority:  1
Rotation:  KScreen::Output::None
Pos:  QPoint(0,0)
MMSize:  QSize(597, 336)
FollowPreferredMode:  false
Size:  QSize(3840, 2160)
Scale:  2
Clones:  None
Mode:  "15"
Preferred Mode:  "15"
Preferred modes:  QList("15")
Modes: 
         "15"    "3840x2160@60"   QSize(3840, 2160)   60
         "16"    "3840x2160@60"   QSize(3840, 2160)   60
         "17"    "3840x2160@60"   QSize(3840, 2160)   59.94
         "18"    "3840x2160@50"   QSize(3840, 2160)   50
         "19"    "3840x2160@30"   QSize(3840, 2160)   30
         "20"    "3840x2160@30"   QSize(3840, 2160)   29.97
         "21"    "3840x2160@24"   QSize(3840, 2160)   24
         "22"    "3840x2160@24"   QSize(3840, 2160)   23.976
         "23"    "2560x1440@120"   QSize(2560, 1440)   120
         "24"    "2560x1440@120"   QSize(2560, 1440)   119.998
         "25"    "2560x1440@60"   QSize(2560, 1440)   60
         "26"    "1920x1080@120"   QSize(1920, 1080)   120.04
         "27"    "1920x1080@120"   QSize(1920, 1080)   120
         "28"    "1920x1080@120"   QSize(1920, 1080)   119.88
         "29"    "1920x1080@60"   QSize(1920, 1080)   60
         "30"    "1920x1080@60"   QSize(1920, 1080)   60
         "31"    "1920x1080@60"   QSize(1920, 1080)   59.94
         "32"    "1920x1080@50"   QSize(1920, 1080)   50
         "33"    "1680x1050@120"   QSize(1680, 1050)   119.986
         "34"    "1680x1050@60"   QSize(1680, 1050)   59.883
         "35"    "1600x900@60"   QSize(1600, 900)   60
         "36"    "1280x1024@75"   QSize(1280, 1024)   75.025
         "37"    "1280x1024@60"   QSize(1280, 1024)   60.02
         "38"    "1440x900@60"   QSize(1440, 900)   59.901
         "39"    "1152x864@75"   QSize(1152, 864)   75
         "40"    "1280x720@60"   QSize(1280, 720)   60
         "41"    "1280x720@60"   QSize(1280, 720)   59.94
         "42"    "1280x720@50"   QSize(1280, 720)   50
         "43"    "1024x768@75"   QSize(1024, 768)   75.029
         "44"    "1024x768@70"   QSize(1024, 768)   70.069
         "45"    "1024x768@60"   QSize(1024, 768)   60.004
         "46"    "800x600@75"   QSize(800, 600)   75
         "47"    "800x600@72"   QSize(800, 600)   72.188
         "48"    "800x600@60"   QSize(800, 600)   60.317
         "49"    "720x576@50"   QSize(720, 576)   50
         "50"    "720x480@60"   QSize(720, 480)   60
         "51"    "720x480@60"   QSize(720, 480)   60
         "52"    "720x480@60"   QSize(720, 480)   59.94
         "53"    "720x480@60"   QSize(720, 480)   59.94
         "54"    "640x480@75"   QSize(640, 480)   75
         "55"    "640x480@73"   QSize(640, 480)   72.809
         "56"    "640x480@67"   QSize(640, 480)   66.667
         "57"    "640x480@60"   QSize(640, 480)   60
         "58"    "640x480@60"   QSize(640, 480)   59.94
         "59"    "640x480@60"   QSize(640, 480)   59.94
         "60"    "720x400@70"   QSize(720, 400)   70.082
EDID Info: 
        Device ID:  "xrandr-Philips Consumer Electronics Company-27M2N5810-WDA2441002495"
        Name:  "27M2N5810"
        Vendor:  "Philips Consumer Electronics Company"
        Serial:  "WDA2441002495"
        EISA ID:  ""
        Hash:  "bba1f59411a6f424423db35c5d7d2aa1"
        Width:  60
        Height:  34
        Gamma:  2.2
        Red:  QQuaternion(scalar:1, vector:(0.681641, 0.308594, 0))
        Green:  QQuaternion(scalar:1, vector:(0.260742, 0.676758, 0))
        Blue:  QQuaternion(scalar:1, vector:(0.139648, 0.0507813, 0))
        White:  QQuaternion(scalar:1, vector:(0.313477, 0.329102, 0))

$ kcmshell6 kcm_kscreen
qrc:/qt/qml/org/kde/kirigami/dialogs/Dialog.qml:301: TypeError: Cannot read property 'height' of null
qrc:/qt/qml/org/kde/kirigami/dialogs/Dialog.qml:142: TypeError: Cannot read property 'height' of null
qrc:/qt/qml/org/kde/kirigami/dialogs/Dialog.qml:300: TypeError: Cannot read property 'width' of null
qrc:/qt/qml/org/kde/kirigami/dialogs/Dialog.qml:150: TypeError: Cannot read property 'width' of null
qrc:/qt/qml/org/kde/kirigami/dialogs/Dialog.qml:300: TypeError: Cannot read property 'width' of null
qrc:/qt/qml/org/kde/kirigami/dialogs/Dialog.qml:150: TypeError: Cannot read property 'width' of null
Comment 13 Oliver Beard 2025-04-09 16:20:18 UTC
When ScreenView's totalSize is (-1, -1), you get an empty view like in the first screenshot. This is consistent with a returned QSize(), which initialises to (-1, -1), so that's probably what's happened there.

When a display is set to mirror itself (nonsense), you appear to get such a value.

We just have to figure out why the backend has this invalid state.

Not sure what causes the cases where you have a single display that's missing but things still align around it, but it's likely there's some funkiness with mirroring/replicas.
Comment 14 Fangru Shao 2025-04-10 13:30:31 UTC
I would try to get inside a livecd environment tomorrow when I am free to see whether it would be normal there and if possible I would also try to reinstall the system to see whether it could be fixed or not.
Comment 15 Oliver Beard 2025-04-10 14:37:08 UTC
(In reply to Fangru Shao from comment #14)
> I would try to get inside a livecd environment tomorrow when I am free to
> see whether it would be normal there and if possible I would also try to
> reinstall the system to see whether it could be fixed or not.

Any information to reproduce this issue from a clean slate would be very helpful — as I'm sure you understand, it's difficult with different hardware.

In particular, the display mirroring steps you take might be important.
Comment 16 Fangru Shao 2025-04-12 04:39:14 UTC
Greetings! I have just tested on a new-installed Arch KDE and surprisingly to find that the external display box is showing normal there. I thought that it could possibly be to problem of EOS but then I enter a EOS livecd and the external is showing normally there. Finally I reinstalled a new EOS system and it is also normal there. Wonder why causes the strange bug I have met.
As for the problem of losing connection, I could reproduce it with the following procedures: 
1. Keep the external monitor connected (Type-C to DP) and reboot, then KDE would lose the detection of it no matter how I replug or turn on/off the power of the monitor.
2. Give the system a reboot one more time, the connection would be back.
To add, if I unplug the monitor before the reboot and then plug it back after the reboot, the detection would be working normally. Using HDMI to HDMI cable would not cause such event.