Created attachment 151306 [details]
Max Refresh-Rate is 30Hz

SUMMARY
When using the open-source Nvidia kernel driver 515.65.01, running Wayland caps the permitted refresh rate to 30Hz rather than the full range of available refresh rates (I'm using a 60Hz display); this issue does not occur with X11


STEPS TO REPRODUCE
1. Using a GPU supported by the open-source Nvidia kernel module, install this driver (515.65.01) if not already installed
2. Reboot to SDDM
3. Select to login with Wayland in SDDM
4. Go to System Settings kcm_kscreen

OBSERVED RESULT
The max permitted refresh rate is half of my display's supported refresh rate

EXPECTED RESULT
I should be able to increase the refresh rate to that of my display (60Hz in this case)

This was said to be fixed in: https://bugs.kde.org/show_bug.cgi?id=442575
but does not appear to be the case here, in my experience.

SOFTWARE/OS VERSIONS
Linux: Arch Linux ( 5.19 kernel )
KDE Plasma Version: 5.25.4
KDE Frameworks Version: 5.96.0
Qt Version: 5.15.5

ADDITIONAL INFORMATION
I have a script in /etc/profile.d/wayland.sh that sets the following:

#! /usr/bin/bash

if [ -x $(command -v loginctl > /dev/null 2>&1) ] && [ -x $(command -v kwin_x11 > /dev/null 2>&1) ]
    if [ loginctl show-session $(loginctl | grep $(whoami) | awk '{print $1}') -p Type | sed 's/Type=//g' != "x11" ]; then

        ## egl for older Nvidia versions
        if ${KWIN_OPENGL_INTERFACE} == "egl"
            export QT_QPA_PLATFORM="wayland-egl"
            export KWIN_DRM_USE_EGL_STREAMS=1
        else

        export QT_QPA_PLATFORM="wayland,xcb"
        fi

        ## Doesn't work for me, for some reason
         # if [ modinfo /usr/lib/modules/$(uname -r)/kernel/drivers/video/nvidia.ko | grep ^version | awk '{print $3}' => 495.44 ]; then
         #    
         # fi
        
        ## GBM for newer Nvidia versions
        # export QT_QPA_PLATFORM="wayland"
        # export QT_QPA_PLATFORMTHEME=qt5ct
    else
        
        export QT_QPA_PLATFORM="xcb"
        
    fi
fi