Congrats dude! You might help hundreds of other users that may be running into the same problem the next days and weeks.
P.S. I don't have an ".xinitrc" at all, as I've just noticed.
However, 'locate' revealed a system-wide xinitrc in /etc/X11/xinit/xinitrc (barely anything essential in there, though)
And there is another 50-systemd-user.sh in .../xinitrc.d/ with only the following line
Code:
systemctl --user import-environment DISPLAY XAUTHORITY
Presumably, Xubuntu and Lubuntu will handle the X Window startup procedure way more differently than it ought to be assumed, considering they're both "just" Ubuntu flavors.