Hi John,
GSP is definitely disabled. It was a fresh install from an ISO, so I’m running pretty stock standard.
I think I might’ve worked out the issue. I noticed in the games I started that the resolution was some bizarre value that was above 4K. The rendering was also a little blurry. I tried messing with the steam launch settings until I realised all games were wrong resolution.
KDE appears to have applied fractional scaling to both my monitors. One is 27” and the other is 32” so I assume there is some logic to make content look physically the same size. One monitor was 150% and the other 175%. That scaling factor seemed to be applied to the incorrect monitor in the game.
So, I made the fractional scaling the same value and my games ran at true 4K, rejoice.
But more importantly… xwayland apps run smooth as butter now. I could tell from the steam splash screen alone, because it has a spinner that has been lagging but is now smooth.
I’ve tested all my other apps and everything is fine. I reverted my Wayland force, and reinstalled a couple of apps I must’ve borked (Spotify, Signal).
So tldr if xwayland is lagging on KDE with Fedora 41… make sure your display scaling is set to the same value on both monitors!