I had the same problem hooking up a NUC to my HDR TV, took me way too long to realise I wasn't in a wayland session!

I'm on opensuse leap, and there's a bug for the no auto-logon with wayland: https://bugzilla.opensuse.org/show_bug.cgi?id=1200436 which links to an SDDM feature to solve it: https://github.com/sddm/sddm/pull/1969

I've just been putting up with manual logons, must have my spiffy HDR :)