Looks to me to be the same issue discussed here: http://community.frame.work/t/fullscreen-games-freeze-on-plasma-6-with-dgpu/
amdgpu.dcdebugmask=0x400 has been working for most of us, which I believe simply disables panel replay. Issue was supposed to be fixed a while ago, but clearly there’s still some problems with it… I personally found building 6.13 myself had no issue but fedora’s rawhide of the same version did have the issue, so maybe a kernel configuration issue? Not sure.