xrandr is Xorg only, it doesn’t work with Wayland. You should be able to make SDDM use your Plasma display configuration - https://wiki.archlinux.org/title/SDDM#Match_Plasma_display_configuration
No clue if that’s going to fix your issues, but at least it’s supposed to work with Wayland.
Yeah, even the TLDR makes it sound more like Qualcomm is yielding to the pressure from OEMs who want to be able to offer longer updates