Can confirm with 24.05 in NixOS:

file:///nix/store/vy0j1a45ix8bsqb90nrd78li5jlnydva-kdeconnect-kde-24.05.0/share/plasma/plasmoids/org.kde.kdeconnect/contents/ui/main.qml:50:25: Type FullRepresentation unavailable

file:///nix/store/vy0j1a45ix8bsqb90nrd78li5jlnydva-kdeconnect-kde-24.05.0/share/plasma/plasmoids/org.kde.kdeconnect/contents/ui/FullRepresentation.qml:63:32: Cannot assign object of type "Action" to property of type "Action_QMLTYPE_98*" as the former is neither the same as the latter nor a sub-class of it.

I also confirm this bug:

file:///usr/share/plasma/plasmoids/org.kde.kdeconnect/contents/ui/main.qml:50:25: Type FullRepresentation unavailable

file:///usr/share/plasma/plasmoids/org.kde.kdeconnect/contents/ui/FullRepresentation.qml:63:32: Cannot assign object of type "Action" to property of type "Action_QMLTYPE_104*" as the former is neither the same as the latter nor a sub-class of it.

Fedora KDE up-to-date (04/06/2024).

(In reply to Leonardo from comment #2)
> I also confirm this bug:
> 
> file:///usr/share/plasma/plasmoids/org.kde.kdeconnect/contents/ui/main.qml:
> 50:25: Type FullRepresentation unavailable
> 
> file:///usr/share/plasma/plasmoids/org.kde.kdeconnect/contents/ui/
> FullRepresentation.qml:63:32: Cannot assign object of type "Action" to
> property of type "Action_QMLTYPE_104*" as the former is neither the same as
> the latter nor a sub-class of it.
> 
> Fedora KDE up-to-date (04/06/2024).

Just to add a bit more information, also the Caveau Plasmoid has this error:

file:///usr/share/plasma/plasmoids/org.kde.plasma.vault/contents/ui/main.qml:102:36: Cannot assign object of type "QQC2.Action" to property of type "Action_QMLTYPE_104*" as the former is neither the same as the latter nor a sub-class of it.

Weather Plasmoid has a similar problem:

file:///nix/store/ivags67m6n8qknkfgjdjw5ir1p3djfbh-kdeplasma-addons-6.0.5/share/plasma/plasmoids/org.kde.plasma.weather/contents/ui/main.qml:452:25: Type FullRepresentation unavailable

file:///nix/store/ivags67m6n8qknkfgjdjw5ir1p3djfbh-kdeplasma-addons-6.0.5/share/plasma/plasmoids/org.kde.plasma.weather/contents/ui/FullRepresentation.qml:38:24: Cannot assign object of type "QQC2.Action" to property of type "Action_QMLTYPE_71*" as the former is neither the same as the latter nor a sub-class of it.

Gonna move this to plasmashell

*** Bug 487464 has been marked as a duplicate of this bug. ***

the suggestion to clear the file `~/.config/plasma-org.kde.plasma.desktop-appletsrc` by user @jimarch here: https://bbs.archlinux.org/viewtopic.php?pid=2176658
successfully let me workaround the issue for the applet org.kde.plasma.weather, though required me to redo my panel setup.

@lasox Thanks for the pointer! I was able to further narrow down the issue to the following part in my plasma-org.kde.plasma.desktop-appletsrc file:

[Containments][1]
ItemGeometries-0x0=Applet-3:2256,64,640,256,0;Applet-72:384,1632,464,464,0;Applet-52:2032,368,1088,352,0;Applet-60:2032,736,1088,688,0;
ItemGeometries-1920x1080=Applet-3:1280,96,640,256,0;Applet-52:832,352,1088,352,0;Applet-60:2032,736,1088,688,0;
ItemGeometries-2560x1440=Applet-3:1920,64,640,256,0;Applet-52:1472,368,1088,352,0;Applet-60:1472,736,1088,608,0;
ItemGeometries-3440x1440=Applet-3:2256,64,640,256,0;Applet-52:2032,368,1088,352,0;Applet-60:2032,736,1088,608,0;
ItemGeometries-3840x1080=Applet-3:2256,64,640,256,0;Applet-52:2032,368,1088,352,0;Applet-60:2032,720,1088,352,0;
ItemGeometries-3840x2160=Applet-3:3200,64,640,256,0;Applet-52:2752,736,1088,352,0;Applet-60:2752,1360,1088,688,0;
ItemGeometries-5120x1440=Applet-3:2256,64,640,256,0;Applet-52:2032,352,1088,352,0;Applet-60:2032,704,1088,624,0;
ItemGeometries-5120x2160=Applet-3:3936,64,640,256,0;Applet-52:3712,736,1088,352,0;Applet-60:3712,1360,1088,688,0;
ItemGeometries-6144x1728=Applet-3:2768,64,640,256,0;Applet-52:2544,511.87,1088,352,0;Applet-60:2544,992,1088,608,0;
ItemGeometries-6982x1964=Applet-3:3184,416,640,256,0;Applet-52:2960,672,1088,320,0;Applet-60:2960,992,1088,608,0;
ItemGeometries-7680x2160=Applet-3:3536,416,640,256,0;Applet-52:3312,720,1088,352,0;Applet-60:3312,1072,1088,688,0;
ItemGeometriesHorizontal=Applet-3:3536,416,640,256,0;Applet-52:3312,720,1088,352,0;Applet-60:3312,1072,1088,688,0;
activityId=ec776d6a-c140-4b16-833b-c1b688cb2794
formfactor=0
immutability=1
lastScreen=0
location=0
plugin=org.kde.plasma.folder
wallpaperplugin=org.kde.image

Simply removing the line `activityId=ec776d6a-c140-4b16-833b-c1b688cb2794` and restarting plasmashell has solved the issue for me. This also ensures that my panels remain configured and functional.

That is strange. Is anyone else who's affected able to fix it by removing the activityId=[something] line from their ~/.config/plasma-org.kde.plasma.desktop-appletsrc file?

(In reply to Nate Graham from comment #8)
> That is strange. Is anyone else who's affected able to fix it by removing
> the activityId=[something] line from their
> ~/.config/plasma-org.kde.plasma.desktop-appletsrc file?

If i use the suggestion above, both problems are fixed for me :)

*** Bug 487597 has been marked as a duplicate of this bug. ***

Can people try deleting ~/.cache/plasmashell/qmlcache/

Potentially related: https://bugreports.qt.io/browse/QTBUG-120189

Please rename the folder instead of deleting it. If that fixes it we'll probably want to look at the cache.

Can confirm the error in Plasma but not in the plasmoidviewer SDK tool.

I don't like how that little Valuts applet imports two namespaces both providing an Action type, although it is unrelated as the error comes from the main.qml which does indeed use import aliases.

A possibly relevant merge request was started @ https://invent.kde.org/plasma/libplasma/-/merge_requests/1146

Git commit d91e9a330eacf673c6c3e18ae218e3d1fb81f7fe by ivan tkachenko.
Committed on 14/06/2024 at 20:36.
Pushed by ratijas into branch 'master'.

PlasmaExtras/PlaceholderMessage: Relax list type to T.Action

Properties should be using Templates version for maximum flexibility.

M  +2    -2    src/declarativeimports/plasmaextracomponents/qml/PlaceholderMessage.qml

https://invent.kde.org/plasma/libplasma/-/commit/d91e9a330eacf673c6c3e18ae218e3d1fb81f7fe

Git commit a66e144315cdd99181c6e1f56d78c10525ca9a67 by ivan tkachenko.
Committed on 16/06/2024 at 09:48.
Pushed by ratijas into branch 'master'.

Relax property types to QtQuick.Templates counterparts

Properties should be using Templates version for maximum flexibility.

See also: https://bugreports.qt.io/browse/QTBUG-120189

M  +3    -2    autotests/wheelhandler/ContentFlickable.qml

https://invent.kde.org/frameworks/kirigami/-/commit/a66e144315cdd99181c6e1f56d78c10525ca9a67

A possibly relevant merge request was started @ https://invent.kde.org/multimedia/elisa/-/merge_requests/592

Git commit ffc7a58b27dbd9742f0958671ad24e20e5de8fb1 by ivan tkachenko.
Committed on 17/06/2024 at 10:23.
Pushed by ratijas into branch 'master'.

Configuration: Replace old style declarative Binding and an oddly specific property

- The standardButton() method is not observable, so it does not matter
  if we use it for a property or in a one-shot onCompleted hook.
- Properties should be using Templates version for maximum flexibility.
  The NOTE on the property technically might be right (for some style
  implementations), but it is completely irrelevant, as the only thing
  we care about here is the Item::enabled property.
- The onCompleted hook is a well established idiom for customizing
  standard buttons in dialog button boxes.

See also: https://bugreports.qt.io/browse/QTBUG-120189

M  +5    -6    src/qml/ConfigurationDialog.qml

https://invent.kde.org/multimedia/elisa/-/commit/ffc7a58b27dbd9742f0958671ad24e20e5de8fb1

Created attachment 170672 [details]
Error seen in Shortcuts KCM

Looks like Kirigami.InlineMessage is also affected, either globally, or at least in the following KCMs, based on screenshots posted to the fedora-kde channel today:
- kcm_keys
- kcm_pulseaudio
- kcm_kscreen
- kcm_bluetooth

Could you investigate and fix those too?

*** Bug 488767 has been marked as a duplicate of this bug. ***

On Manjaro, all the following pages are broken in Plasma system settings:

Keyboard>Shortcuts
Sound
Display & Monitor
Bluetooth
Printers
Wifi & Internet> Firewall
Remote Desktop
Wallpaper
All Colors and Themes sub pages
Text & Fonts > Fonts
Notifications
Windows Management > Desktop Effects, Windows Rules, Scripts, Virtual Desktops
General Behavior
All Search sub pages
Application Permissions
User Feedback
Region & Language
Power Management
Autostart
Session> Desktop Session

*** Bug 488907 has been marked as a duplicate of this bug. ***

I encountered this problem over at Bug 488907, and was directed to upload a backup of my `~/.cache/plasmashell/qmlcache` that was producing the error. I will do so after posting this comment (unsure if I can do it alongside a comment).

So to be clear, the qmlcache archive I am uploading contains the backed up `~/.cache` folder from the time when the issue was occurring. I backed up the folder and then removed the original `~/.cache`.

Created attachment 170780 [details]
Archive containing qmlconfg files

Archive of ~/.cache/plasmashell/qmlconfig from when the issue was occurring

I still have the backup of my entire `~/.cache` folder and will keep it around, let me know if there is any more information I can help provide!

The bug is not critically affecting me, but it may be critically affecting others, and I am happy to help.

Thanks so much, please do keep it around for a while!

After some upgrades, the problem became reproducible only in the first launch of Plasma settings after a fresh login, so after closing and reopening Plasma settings the problem is gone.

*** Bug 488326 has been marked as a duplicate of this bug. ***

(Coming from bug 489022, what a long duplicate chain...)

Further test results on system settings modules (on Arch Linux, 2024-06-23):
1. After a fresh login, open system settings and click on "Sound": Working for me
2. Open system settings, click on any "affected modules" (see bug 489022): Working for me
3. Open system settings, click on "Mouse & Touchpad", then click on any "affected modules": Error
4. Open system settings, click on any "affected modules", then click on "Mouse & Touchpad", then click on any "affected modules" OTHER THAN "Sound": Working for me
5. Open system settings, click on any "affected modules", then click on "Mouse & Touchpad", then click on "Sound": Crash
6. Open system settings, click on any "unaffected modules", then do any one of 2--5: The same result as 2--5

Clearing (moving) ~/.cache/plasmashell/qmlconfig doesn't work for me.

(In reply to Huanyu Liu from comment #30)
> Clearing (moving) ~/.cache/plasmashell/qmlconfig doesn't work for me.

That will fix the issue for plasmashell, but not systemsettings. For that, it's ~/.cache/systemsettings /qmlconfig. But please don't delete it; move it elsewhere, and then if that fixes the issue, archive it and attach it here. Thanks!

Hi - I moved the ~/.cache/systemsettings folder and can reproduce exactly as https://bugs.kde.org/show_bug.cgi?id=487904#c30 described - will attach a crashreport (which did not happen before - up till now only the error messages appeared for me)

Created attachment 170869 [details]
DrKonqi Crash report

Opened systemsettings - clicked on "Sound", then "Mouse & Touchpad" - "Mouse" and then again "Sound"  which produced the crash

The crash when returning to the Sound page is a different bug which is already fixed in Qt 6.7.2.

(In reply to Nate Graham from comment #31)
> (In reply to Huanyu Liu from comment #30)
> > Clearing (moving) ~/.cache/plasmashell/qmlconfig doesn't work for me.
> 
> That will fix the issue for plasmashell, but not systemsettings. For that,
> it's ~/.cache/systemsettings /qmlconfig. But please don't delete it; move it
> elsewhere, and then if that fixes the issue, archive it and attach it here.
> Thanks!

Moved ~/.cache/systemsettings/qmlconfig and the error message persists.

*** Bug 489064 has been marked as a duplicate of this bug. ***

Fixed for me by Archs' QT6 update today from 6.7.1 -> 6.7.2 :)

The QML error is gone after upgrading to Qt 6.7.2

(In reply to medin from comment #38)
> The QML error is gone after upgrading to Qt 6.7.2

It is still there if you click on mouse an trackpad an then go to a affected setting. 

Operating System: Garuda Linux (Arch)
KDE Plasma Version: 6.1.0
KDE Frameworks Version: 6.3.0
Qt Version: 6.7.2
Kernel Version: 6.9.6-1-cachyos (64-bit)
Graphics Platform: Wayland

Created attachment 171105 [details]
systemsettings QML cache folder

I have a 100% reproducible case for this bug:

1. Run `systemsettings kcm_networkmanagement`
2. Within System Settings, navigate to the Mouse KCM 

It fails to load with this error:

kf.kcmutils: Error loading QML file qrc:/kcm/kcm_mouse/main.qml
kf.kcmutils:     qrc:/kcm/kcm_mouse/main.qml:52:13: Type Header unavailable
        header: Header {
                ^
kf.kcmutils:     qrc:/kcm/kcm_mouse/Header.qml:19:5: Type Message unavailable
        Message {
        ^
kf.kcmutils:     qrc:/kcm/kcm_mouse/Message.qml:13:1: Type Kirigami.InlineMessage unavailable
    Kirigami.InlineMessage {
    ^
kf.kcmutils:     file:///home/nate/kde/usr/lib64/qml/org/kde/kirigami/InlineMessage.qml:63:1: Type KT.InlineMessage unavailable
    KT.InlineMessage {
    ^
kf.kcmutils:     qrc:/qt/qml/org/kde/kirigami/templates/InlineMessage.qml:123:43: Cannot assign object of type "TP.IconPropertiesGroup" to property of type "IconPropertiesGroup_QMLTYPE_102*" as the former is neither the same as the latter nor a sub-class of it.
        property TP.IconPropertiesGroup icon: TP.IconPropertiesGroup {}
                                              ^

Deleting the entire ~/.cache folder does not help, so I'm thinking this may not actually be a caching issue at all. However just in case, I'm attaching my systemsettings QML cache folder

Created attachment 171133 [details]
Non-reproduction of #c40.

(In reply to Nate Graham from comment #40)
If of use, it doesn't appear to be reproducible for me - I invoked `systemsettings kcm_networkmanagement`, then used search to navigate to "Mouse".

Operating System: Fedora Linux 40
KDE Plasma Version: 6.1.1
KDE Frameworks Version: 6.3.0
Qt Version: 6.7.1
Kernel Version: 6.9.6-200.fc40.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 12 × AMD Ryzen 5 7600X 6-Core Processor
Memory: 30.5 GiB of RAM
Graphics Processor: AMD Radeon RX 5700
Manufacturer: ASRock
Product Name: X670E Taichi

*** Bug 489037 has been marked as a duplicate of this bug. ***

*** Bug 489022 has been marked as a duplicate of this bug. ***

*** Bug 488776 has been marked as a duplicate of this bug. ***

*** Bug 488810 has been marked as a duplicate of this bug. ***

*** Bug 488899 has been marked as a duplicate of this bug. ***

*** Bug 488945 has been marked as a duplicate of this bug. ***

*** Bug 488965 has been marked as a duplicate of this bug. ***

*** Bug 488985 has been marked as a duplicate of this bug. ***

*** Bug 489018 has been marked as a duplicate of this bug. ***

I had to do some course project that requires long-time code running recently, so I didn't upgrade my system last week. Today, I did a full upgrade, and Comment 30 is no longer reproducible. Comment 40 was not reproducible for me from the beginning.

Operating System: Arch Linux 
KDE Plasma Version: 6.1.1
KDE Frameworks Version: 6.3.0
Qt Version: 6.7.2
Kernel Version: 6.9.7-arch1-1 (64-bit)
Graphics Platform: Wayland

A possibly relevant merge request was started @ https://invent.kde.org/plasma/plasma-nm/-/merge_requests/361

A possibly relevant merge request was started @ https://invent.kde.org/plasma/systemsettings/-/merge_requests/322

A possibly relevant merge request was started @ https://invent.kde.org/plasma/plasma-desktop/-/merge_requests/2358

I've broken out this issue into three, since there seem to be multiple related but distinct issues at play:

Widgets with PlasmaExtras.PlaceholderMessage using a QQC2.Action in it (seen so far: KDEconnect, Weather, Vaults): Bug 487464

When you open System Settings directly on the Mouse or Networks KCM, and then navigate to another one of those KCMs, they break: Bug 488326

KCMs with any InlineMessages or a KNewStuff dialog break in System Settings but work in KCMShell6: Bug 488965

This specific issue is a duplicate of Bug 487464, marking accordingly.

*** This bug has been marked as a duplicate of bug 487464 ***