I use ddcutil all the time on linux to set my monitor brightness without needing to fiddle with the OSD.
https://www.ddcutil.com/#ddcui
Also, if you have ddcci-driver-linux installed, then the KDE desktop lets you adjust monitor brightness from the UI. Eventually Linux upstream might get the same functionality as the out-of-tree module.
systemctl --user edit plasma-powerdevil.service
[Service]
Environment="POWERDEVIL_NO_DDCUTIL=1"
EDIT: I tried switching to Wayland on Arc and am getting stuttery mouse cursor movement at around 36 FPS. I wonder what's wrong...