Dual-monitor lagging with laptop


I’m using NixOS unstable with Plasma 6. I’m using the Wayland backend with an optimus laptop and the external display is truly lagging and I can’t figure why. It’s just not smooth, but running GLX gears report the correct framerate.

The integrated GPU is provided by the Intel CPU (i7-12650H) and the discrete GPU is a RTX 4070.

The integrated screen is at 144Hz and the external display 100Hz. I have tried a lot of options (the open driver or the default, reverseSync and sync mode, etc…) without any success: the second monitor always seems to be lagging/not smooth. The integrated one, on the other hand, is perfectly fine.

Has anyone had such issue with Plasma ? If so, have you any advices ?

What I already tried:

  • Tried the open driver and the default one
  • Tried sync and reverseSync
  • Tried to shutdown the integrated screen or not
  • Tried to put both screens at 60Hz and the external one still seemed to be “laggy”