I've got similar hardware here - and just pulled down all my updates on the Fedora33 KDE spin. So far, both GTK and QT windows/UI are behaving fine for me...

Some some relevant hardware/kernel info I yanked out of glxinfo.

I've not looked for any bugreports, but I'm happy to follow one if I might be useful.

  AMD Radeon RX 5700 XT (NAVI10, DRM 3.40.0, 5.11.16-200.fc33.x86_64, LLVM 11.0.0)
  OpenGL version string: 4.6 (Compatibility Profile) Mesa 20.3.5

  Monitors: 2
 0: +*DisplayPort-0 1920/598x1080/336+0+420  DisplayPort-0
 1: +DisplayPort-1 1080/598x1920/336+1920+0  DisplayPort-1