Dear Maintainer, this described bug seems to happen only on Wayland.
I also launched KDE Plasma 6.3 on Debian/testing on Xorg, where the execution of applications from Games or the last category do work!
I also already created an all new guest user with newly created home folder, with which the problem on Wayland persists.
Thank you for your attention.I also noticed this bug already in the #debian-next channel on OFTC IRC, already once.
Adrian Kiess
