I tried it with multiple distros ( Fedora / Arch / Ubuntu … ) and with the latest KDE Plasma.
If I go to “Get New” in the System Settings → Global Themes to Download a new Theme and I download Utterly Sweet,
the Desktop becomes pitch black without a Taskbar as soon as apply the newly downloaded Theme.
I executed systemsettings from a terminal to see what’s happening:
qrc:/kcm/kcm_lookandfeel/main.qml:144:5: QML OverlaySheet: Binding loop detected for property “implicitHeight”:
file:///usr/lib64/qt6/qml/org/kde/kirigami/templates/OverlaySheet.qml:132:5
qrc:/kcm/kcm_lookandfeel/main.qml:144:5: QML OverlaySheet: Binding loop detected for property “implicitHeight”:
file:///usr/lib64/qt6/qml/org/kde/kirigami/templates/OverlaySheet.qml:132:5
qrc:/kcm/kcm_lookandfeel/main.qml:144:5: QML OverlaySheet: Binding loop detected for property “implicitHeight”:
file:///usr/lib64/qt6/qml/org/kde/kirigami/templates/OverlaySheet.qml:132:5
Now I tried installing the Plasma 6 version as a tar.gz and it turns everything Pitch Black first but after a reboot it works fine. So the only problem is the “pitch black” thing. Please take a look at the attached LOG. It shows some Qt-specific issues in two files: OverlaySheet.qml and main.qml. I think this is either a KDE-specific or a Qt6-specific issue …
In all this time I never installed a global theme. I prefer my own stuff anyway. But. I’ve seen some weird stuff in those third party theming stuff. Especially those that come with scripts. And this one has some like, for example, the window buttons applet ( which contain a “main.qml”) That’s why I suggested to install everything separately. But hey, you have it working.