It would be great if SDDM could run under wayland. Documentation of SDDM says, that SDDM is abble to run under wayland. It's a little inappropriate to run Xorg to run wayland session. It would be great if x11-misc/sddm had USE flag, which can change default configuration to run SDDM under (for example) kwin compositor. If this is not possible, it would be a good idea to run SDDM under X11 without root privileges. This way is for sure stable.
It is experimental and broken for every second user trying to use it.
https://github.com/gentoo/qt/pull/267 was where we did some WIP on it, just for completeness.
One of the reasons for SDDM Wayland backend currently failing to work is bug 935166. And prior to 0.21.0 it would have required weston[fullscreen] instead, dependency on which was likewise not enforced by the old ebuild for 0.18 or 0.20 series either. Once the correct dependency on dev-libs/weston with the appropriate shell is enforced, it's very likely that SDDM will work reliably with the Wayland backend, since ultimately it's using much of the same graphical stack that most of the still widely used Xorg DDX do (at least with Intel and AMD graphics that I'm familiar with). I expect enabling the Wayland backend by default is not going to be far away. And, unless I'm mistaken, other Plasma 6 distros such as Arch Linux already do use Qt6 SDDM with the Wayland backend as the default.
I just realized that the Arch system without xorg-server also lacks sddm, so they likely have not migrated their package to Wayland backend by default. Sorry for that bit of misinformation previously.
