The Window Switcher installation is broken, resources are missing.
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When using Alt+Tab to switch window:
The Window Switcher installation is broken, resources are missing. Contact your distribution about this.
In addition, the desktop effects are not working.
Go to KDE systemsettings > Hardware > Display and Monitor > Compositor > Uncheck "Enable compositor at start up".
$ qdbus org.kde.KWin /KWin supportInformation
Compositing is active
Compositing Type: OpenGL