hey i had the same problem which occured a week ago that i “fixed” just yesterday, made a post here. my theory is that there was a mesa update that is conflicting with SDDM at the moment, which was NOT updated. this isnt exclusive to arch, it happened on other distro’s for me and others as well! disabling SDDM service (via chroot) and using other DM (e.g. ly) worked for me!