SUMMARY

When using any Jetbrains IDE, the desktop in general becomes laggy, to the point of being unusable for certain tasks. The easiest example I can find is to move the cursor over the Task Manager (provided it displays the thumbnail of the window when hovering it). But it also affects things like dragging files or text, reproducing videos on VLC, or almost anything that makes a floating window (like a tooltip, a menu or a thumbnail) show up.

This could be either a bug caused by Jetbrains' IDEs or Plasma itself, but figured out I'd post it here because:
1. This didn't happen using the same version of their software in Plasma 5.
2. This doesn't happen in any other DE that I've tried (Gnome and LXQt).

Bug described originally here: https://youtrack.jetbrains.com/issue/JBR-6830/Poor-performance-with-KDE-Plasma-6-X11

STEPS TO REPRODUCE
1. Use Plasma X11
2. Open any Jetbrains IDE
3. Have the Task Manager thumbnails on hover enabled.

OBSERVED RESULT
The cursor starts skipping frames and becoming noticeable slower.

EXPECTED RESULT
Cursor moving normally without lagging. 

SOFTWARE/OS VERSIONS
Linux: 6.8.1-arch1-1 (64 bits)
KDE Plasma Version: 6.0.2
KDE Frameworks Version: 6.0.0
Qt Version: 6.6.2
JetBrains Rider: 2023.3.4