Ok, back to the task at hand then. Using SDDM again, please attempt to start a Plasma X11 session from the login screen. From what you’ve posted previously this will fail and you’ll end up back at the login screen. Switch to a console VT, login, and capture the journal log (as already explained) so that it is saved to a file.
If you switch back to the display manager VT, you should be able to launch a working Plasma Wayland desktop right? Anyway, upload the out.log content to susepaste so that it can be reviewed here. The timestamps should help you to know that the output is relevant to the Plasma X11 launch attempt.