plasma-discover 
QQmlApplicationEngine failed to load component
qrc:/qml/DiscoverWindow.qml:219:9: Type Kirigami.OverlaySheet unavailable
file:///usr/lib/qt5/qml/org/kde/kirigami.2/OverlaySheet.qml:21:1: Type T.OverlaySheet unavailable
file:///usr/lib/qt5/qml/org/kde/kirigami.2/templates/OverlaySheet.qml:697:25: Non-existent attached object
org.kde.plasma.discover: Errors when loading the GUI
org.kde.plasma.discover: could not get the main object

Probably kirigami 5.97 breaks it.

Kirigami is already patched (since it also broke Calamares, and scrollbars in systemsettinsg & neochat). Are you on the build repo? If not, then please install it with sudo pacman -U http://kaosx.tk/repo/build/kirigami-5.97.0-3-x86_64.pkg.tar.zst. It will probably move today to all users.
One bug report was open for the commit that breaks all in kirigami, but upstream closed it right away, so no other option than to patch and revert the breaking changes.
https://github.com/KaOSx/apps/commit/e7fe2ade93a817b5ed8b6e4700f0cbf38d58f877
Breaking commit:
https://invent.kde.org/frameworks/kirigami/-/commit/c28dff79721d3805edcd413ef233216b3b3b0104