Thanks for asking, I should have mentioned the posts I was reading for tinkering. I guess I quickly read through many other posts here but I forgot them so maybe only took bits and pieces here and there as grains of salt.
been mostly reading up what these guys posted. mostly the first guy.
if you are curious how I start the separate DE env that spawns a new display on :1 and wayland-1 then this is the command I used for spawning the new KDE plasma DE display window:
sudo incus exec kde-container -- sudo -u user bash -c 'source /home/user/.profile && dbus-run-session /usr/bin/startplasma-wayland'
by “easily” that is subjective, definitely went through hoops and tried my best to read the incus docs and other associated programs man pages when I could. do I remember it all not really but I tried my best, haha. didn’t really copy paste anything over expecting it to just work, I made sure I looked through each option carefully in a way that I could. seemingly running the /usr/bin/startplasma-wayland that starts a window for controlling this separate Display/DE is the most stable. however, since running on my host’s display is mostly stable, it is was what I really ended up choosing. the Kwin wayland drm hanging error is the only clue I have. only seems to occur for this specific app that is running on Xwayland with that QT5 xcb env flag set. running the app under wayland is just a graphical nightmare with the submenus popping out as new windows and other oddities I might have not noticed or come across.(happens when running natively wayland on host too, so not a container issue, the app probably only works with X)
I was thinking. the first link has the guy using X1 for the X socket but he still uses the host’s wayland-0? idk maybe I should keep X on a separate socket connection. just a thought