Right clicking on a icon-only task manager button so that you can pin an app or do some other action does not work in Wayland because the window thumbnail preview covers the right-click menu. Observed in Arch Linux and KDE Neon User Stable on Wayland.
STEPS TO REPRODUCE
1. Right click a icons-only task manager button
2. Observe the window thumbnail popups covers the right click menu
The window thumbnails should not popup if you've right clicked on the window button to access the app pinning and new instance options.
Operating System: Arch Linux
KDE Plasma Version: 5.20.3
KDE Frameworks Version: 5.76.0
Qt Version: 5.15.2
Kernel Version: 5.9.10-zen1-1-zen
OS Type: 64-bit
Processors: 4 × Intel® Core™ i3-10110U CPU @ 2.10GHz
Memory: 15.5 GiB of RAM
Graphics Processor: Mesa Intel® UHD Graphics
Created attachment 135309 [details]
Can confirm on KDE Plasma 5.20.90
Since there is no problem in X11, I think component should be kwin (wayland-generic).
I'll save Nate some work as this is another duplicate of #417939. :)
*** This bug has been marked as a duplicate of bug 417939 ***