Apparently, when using gdm3 (the default of Ubuntu 18.04) we should be able to run
gdmflexiserver to get a new greeter and log in with resp. switch to another user.
When running the command in my i3 session, I get
$ gdmflexiserver Could not identify the current session.
The problem seems to be that
XDG_SESSION_COOKIE is not set:
$ env | grep "XDG" XDG_VTNR=2 XDG_SESSION_ID=3 XDG_SESSION_TYPE=x11 XDG_DATA_DIRS=/usr/share/i3:/usr/local/share:/usr/share:/var/lib/snapd/desktop XDG_SESSION_DESKTOP=i3 XDG_CURRENT_DESKTOP=i3 XDG_SEAT=seat0 XDG_RUNTIME_DIR=/run/user/1000 XDG_CONFIG_DIRS=/etc/xdg/xdg-i3:/etc/xdg
How can I make the gdm3-i3 combo set
XDG_SESSION_COOKIE during login (or whenever appropriate)?