SUMMARY The effect is enabled in the settings of the Task Manager, but it does nothing on Wayland. SOFTWARE/OS VERSIONS KDE Plasma Version: 5.20.2 KDE Frameworks Version: 5.75.0 Qt Version: 5.15.1 ADDITIONAL INFORMATION Intel UHD 620 video card. It doesn't matter whether the Intel driver is installed, and which rendering backend is chosen in the Compositing settings.
Can you clarify what effect you're talking about? Are you talking about window thumbnails not showing up? A screenshot that shows what's missing would be helpful/
Created attachment 133412 [details] XOrg (working)
Created attachment 133413 [details] Wayland (not working)
Sorry for the lack of detail. Go to Configure Task Manager, and check 'Highlight windows when hovering over tasks'. I attached screenshots of what it looks like on X11 (where it works) and on Wayland (where it doesn't).
Ah that! Thanks for the screenshots and the clarifications.
*** This bug has been marked as a duplicate of bug 433134 ***