Firefox takes a long time to go fullscreen — both when watching YouTube and when pressing F11.
This only happens on Wayland when the screen resolution is set to something other than the native one.
At the native resolution, it works fine.
Under X11, fullscreen works fine at any resolution.
Chrome doesn’t have this problem.
Graphics card: Radeon HD 6570. 24" Dell monitor connected via DVI.
Hi - to help folks best guide you, could you please provide your basic system information from the Info Center app? The Copy Details button is the easiest way to get that ready to paste in:
Is a bit faster type in konsole kinfo and copy the info. 
Regards
kinfo show me:
Operating System: KDE neon 6.3
KDE Plasma Version: 6.3.4
KDE Frameworks Version: 6.12.0
Qt Version: 6.8.2
Kernel Version: 6.11.0-21-generic (64-bit)
Graphics Platform: Wayland
Processors: 4 × AMD Athlon™ X4 740 Quad Core Processor
Memory: 7.7 GiB of RAM
Graphics Processor: AMD TURKS