I can confirm this issue for the X11 session, but not with Wayland (openSUSE Tumbleweed with KDE Plasma Version: 6.0.2, KDE Frameworks Version: 6.0.0, Qt Version: 6.6.2).

Probably due to https://invent.kde.org/plasma/plasma-desktop/-/commit/12ac086128c7e7db831f35d53616db0d6823fd90

(In reply to Frank Kruger from comment #2)
> Probably due to
> https://invent.kde.org/plasma/plasma-desktop/-/commit/
> 12ac086128c7e7db831f35d53616db0d6823fd90

JFYI: After removing the synaptics touchpad driver, the issue described here (for X11) is solved.

But libinput driver doesn't support kinetic scroll, only synaptics driver does :(

I can confirm this bug and the fix on my Dell XPS with Solus.

I had xorg-driver-input-synaptics installed because in Plasma 5, it was necessary to enable all options for my touchpad.
After I updated the system to Plasma 6, I had the same symptom as described, in the Touchpad settings I saw "No touchpad found" 

```
❯ kcmshell6 kcm_touchpad
qt.qml.typeresolution.cycle: Cyclic dependency detected between "qrc:/qt/qml/org/kde/desktop/private/TextFieldContextMenu.qml" and "qrc:/qt/qml/org/kde/desktop/MenuItem.qml"
qrc:/libinput/touchpad.qml:691: TypeError: Cannot read property 'supportsScrollFactor' of null
```

After uninstalling xorg-driver-input-synaptics and rebooting, I now see all settings in the Touchpad settings.

So, is this a bug or working as intended? On Void Linux I cannot install `xf86-input-synaptics` because it is part of `xorg-input-drivers` meta package, so I would like to know fist before I go and bother the Void maintainers.

I have the same issue here with Plasma 6.1.0, Frameworks 6.3.0, Qt 6.7.2, on X11 and kernel 6.9.5 (amd64).

I have the same issue when I start systemsettings with my usual LOCALE env variables : 

CSF_LANGUAGE=us
LANG=fr_FR.UTF-8
LANGUAGE=
LC_COLLATE=C
LC_MEASUREMENT=C
LC_MONETARY=C
LC_NUMERIC=C
LC_TIME=C
LC_CTYPE=fr_FR.UTF-8

When I use LC_ALL=C, Then the page show.

Here the logs when using my locales :

qt.qpa.wayland: eglSwapBuffers failed with 0x300d, surface: 0x0
qrc:/qt/qml/org/kde/systemsettings/CategoryItem.qml:31:13: Unable to assign IconPropertiesGroup_QMLTYPE_101 to IconPropertiesGroup_QMLTYPE_101
qrc:/qt/qml/org/kde/systemsettings/CategoryItem.qml:31:13: Unable to assign IconPropertiesGroup_QMLTYPE_101 to IconPropertiesGroup_QMLTYPE_101
qrc:/qt/qml/org/kde/systemsettings/CategoryItem.qml:31:13: Unable to assign IconPropertiesGroup_QMLTYPE_101 to IconPropertiesGroup_QMLTYPE_101
qml: Page SubCategoryPage_QMLTYPE_113(0x5c74e1420190) is already in the PageRow
qml: Pushed pages do not conform to the rules. Please check the documentation.
qml: push (file:///usr/lib/qt6/qml/org/kde/kirigami/PageRow.qml:223)
onActiveSubCategoryRowChanged (qrc:/qt/qml/org/kde/systemsettings/SubCategoryPage.qml:180)
expression for onClicked (qrc:/qt/qml/org/kde/systemsettings/CategoriesPage.qml:207)
qrc:/ui/main.qml:378: TypeError: Cannot read property 'buttonMapping' of null
qrc:/ui/main.qml:339: TypeError: Cannot read property 'isAnonymousInputDevice' of null
qrc:/ui/main.qml:273: TypeError: Cannot read property 'isAnonymousInputDevice' of null
qrc:/ui/main.qml:70: TypeError: Cannot read property 'isAnonymousInputDevice' of null
qrc:/ui/main.qml:45: TypeError: Cannot read property 'isAnonymousInputDevice' of null
qrc:/ui/main.qml:48: TypeError: Cannot read property 'inputDevices' of null
qrc:/ui/main.qml:39: TypeError: Cannot read property 'inputDevices' of null
qrc:/ui/main.qml:25: TypeError: Cannot read property 'inputDevices' of null
kcm_touchpad: Using KWin+Wayland backend
kcm_touchpad: Touchpad found: "SynPS/2 Synaptics TouchPad" ("event6")
qrc:/libinput/touchpad.qml:70:13: Type Kirigami.InlineMessage unavailable 
         header: Kirigami.InlineMessage { 
                 ^
file:///usr/lib/qt6/qml/org/kde/kirigami/InlineMessage.qml:63:1: Type KT.InlineMessage unavailable 
     KT.InlineMessage { 
     ^
qrc:/qt/qml/org/kde/kirigami/templates/InlineMessage.qml:123:43: Cannot assign object of type "TP.IconPropertiesGroup" to property of type "IconPropertiesGroup_QMLTYPE_101*" as the former is neither the same as the latter nor a sub-class of it. 
         property TP.IconPropertiesGroup icon: TP.IconPropertiesGroup {} 
                                               ^
qml: Page SubCategoryPage_QMLTYPE_113(0x5c74e1420190) is already in the PageRow
qml: Pushed pages do not conform to the rules. Please check the documentation.
qml: push (file:///usr/lib/qt6/qml/org/kde/kirigami/PageRow.qml:223)
onActiveSubCategoryRowChanged (qrc:/qt/qml/org/kde/systemsettings/SubCategoryPage.qml:180)
expression for onClicked (qrc:/qt/qml/org/kde/systemsettings/SubCategoryPage.qml:215)

(Actually, the logs are not relevant since the same output occur with LC_ALL=C

(In reply to Flav from comment #8)
> I have the same issue when I start systemsettings with my usual LOCALE env
> variables : 
> 
> CSF_LANGUAGE=us
> LANG=fr_FR.UTF-8
> LANGUAGE=
> LC_COLLATE=C
> LC_MEASUREMENT=C
> LC_MONETARY=C
> LC_NUMERIC=C
> LC_TIME=C
> LC_CTYPE=fr_FR.UTF-8
> 
> When I use LC_ALL=C, Then the page show.
> 
> Here the logs when using my locales :
> 
> qt.qpa.wayland: eglSwapBuffers failed with 0x300d, surface: 0x0
> qrc:/qt/qml/org/kde/systemsettings/CategoryItem.qml:31:13: Unable to assign
> IconPropertiesGroup_QMLTYPE_101 to IconPropertiesGroup_QMLTYPE_101
> qrc:/qt/qml/org/kde/systemsettings/CategoryItem.qml:31:13: Unable to assign
> IconPropertiesGroup_QMLTYPE_101 to IconPropertiesGroup_QMLTYPE_101
> qrc:/qt/qml/org/kde/systemsettings/CategoryItem.qml:31:13: Unable to assign
> IconPropertiesGroup_QMLTYPE_101 to IconPropertiesGroup_QMLTYPE_101
> qml: Page SubCategoryPage_QMLTYPE_113(0x5c74e1420190) is already in the
> PageRow
> qml: Pushed pages do not conform to the rules. Please check the
> documentation.
> qml: push (file:///usr/lib/qt6/qml/org/kde/kirigami/PageRow.qml:223)
> onActiveSubCategoryRowChanged
> (qrc:/qt/qml/org/kde/systemsettings/SubCategoryPage.qml:180)
> expression for onClicked
> (qrc:/qt/qml/org/kde/systemsettings/CategoriesPage.qml:207)
> qrc:/ui/main.qml:378: TypeError: Cannot read property 'buttonMapping' of null
> qrc:/ui/main.qml:339: TypeError: Cannot read property
> 'isAnonymousInputDevice' of null
> qrc:/ui/main.qml:273: TypeError: Cannot read property
> 'isAnonymousInputDevice' of null
> qrc:/ui/main.qml:70: TypeError: Cannot read property
> 'isAnonymousInputDevice' of null
> qrc:/ui/main.qml:45: TypeError: Cannot read property
> 'isAnonymousInputDevice' of null
> qrc:/ui/main.qml:48: TypeError: Cannot read property 'inputDevices' of null
> qrc:/ui/main.qml:39: TypeError: Cannot read property 'inputDevices' of null
> qrc:/ui/main.qml:25: TypeError: Cannot read property 'inputDevices' of null
> kcm_touchpad: Using KWin+Wayland backend
> kcm_touchpad: Touchpad found: "SynPS/2 Synaptics TouchPad" ("event6")
> qrc:/libinput/touchpad.qml:70:13: Type Kirigami.InlineMessage unavailable 
>          header: Kirigami.InlineMessage { 
>                  ^
> file:///usr/lib/qt6/qml/org/kde/kirigami/InlineMessage.qml:63:1: Type
> KT.InlineMessage unavailable 
>      KT.InlineMessage { 
>      ^
> qrc:/qt/qml/org/kde/kirigami/templates/InlineMessage.qml:123:43: Cannot
> assign object of type "TP.IconPropertiesGroup" to property of type
> "IconPropertiesGroup_QMLTYPE_101*" as the former is neither the same as the
> latter nor a sub-class of it. 
>          property TP.IconPropertiesGroup icon: TP.IconPropertiesGroup {} 
>                                                ^
> qml: Page SubCategoryPage_QMLTYPE_113(0x5c74e1420190) is already in the
> PageRow
> qml: Pushed pages do not conform to the rules. Please check the
> documentation.
> qml: push (file:///usr/lib/qt6/qml/org/kde/kirigami/PageRow.qml:223)
> onActiveSubCategoryRowChanged
> (qrc:/qt/qml/org/kde/systemsettings/SubCategoryPage.qml:180)
> expression for onClicked
> (qrc:/qt/qml/org/kde/systemsettings/SubCategoryPage.qml:215)

Mabe you are (also) hit by https://bugs.kde.org/show_bug.cgi?id=488326.

I can reproduce this on the following system:

Operating System: Arch Linux 
KDE Plasma Version: 6.1.4
KDE Frameworks Version: 6.5.0
Qt Version: 6.7.2
Kernel Version: 6.10.7-arch1-1 (64-bit)
Graphics Platform: Wayland
Processors: 4 × Intel® Pentium® CPU 4425Y @ 1.70GHz
Memory: 7.6 GiB of RAM
Graphics Processor: Mesa Intel® UHD Graphics 615
Manufacturer: Microsoft Corporation
Product Name: Surface Go 2
System Version: 1

The touchpad of my surface type cover does show up as a mouse instead of a touchpad in the settings.

JFYI: If the issue described here is related to bug 488326, it will be fixed with Frameworks 6.6.