For anyone curious:
Non-functional black-screen-with-pointer X: $ echo $XDG_DATA_DIRS :/var/lib/snapd/desktop
Workaround second X with plasma: $ echo $XDG_DATA_DIRS /usr/share//usr/share/xsessions/plasma:/usr/local/share/:/usr/share/:/var/lib/snapd/desktop
After fully removing snapd: $ echo $XDG_DATA_DIRS /usr/share:/usr/share:/usr/local/share
For anyone curious:
Non-functional black-screen- with-pointer X: snapd/desktop
$ echo $XDG_DATA_DIRS
:/var/lib/
Workaround second X with plasma: /usr/share/ xsessions/ plasma: /usr/local/ share/: /usr/share/ :/var/lib/ snapd/desktop
$ echo $XDG_DATA_DIRS
/usr/share/
After fully removing snapd: /usr/share: /usr/local/ share
$ echo $XDG_DATA_DIRS
/usr/share: