Problem:
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.
Possible solution:
Go to KDE systemsettings > Hardware > Display and Monitor > Compositor > Uncheck "Enable compositor at start up".
$ qdbus org.kde.KWin /KWin supportInformation
Compositing
===========
Compositing is active
Compositing Type: OpenGL
#8937