Created attachment 136245 [details]
Screenshot of oberved result with dolphin

SUMMARY
When using the task manager under wayland, the preview shown when hovering over an icon should show a window. In wayland there is no window preview inside of the popup box.

Although 429568 may sound similar to this, this occurs in all applications and not just dolphin. I have tested and this occurs with dolphin, firefox, intellij-idea-ce and konsole.

STEPS TO REPRODUCE
1. Open application, try dolphin.
2. Hover over dolphin icon in task manager
3. Wait till preview opens

OBSERVED RESULT
Preview popup shows but no window preview is present

EXPECTED RESULT
Window preview should be shown

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch Linux Kernel 5.11.2
(available in About System)
KDE Plasma Version: 5.21.1
KDE Frameworks Version: 5.79.0
Qt Version: 5.12.2
Graphics Platform: Wayland

ADDITIONAL INFORMATION
Using Intel Mesa Graphics.