How to reproduce
$ sudo apt install ./Minecraft.deb
Application Launcher > Applications > Games > Minecraft Launcher
The launcher works fine on GNOME.
MCL-10080
Window glitches on KDE Plasma
Resolved
Fixed
0
What do you mean by window content?
The only odd thing I see is the frame, and the frame is not window content. There is not a single line of code that would be responsible for drawing a window frame in the entire launcher codebase. It's the responsibility of your window manager/compositor.