Comment 2 for bug 1704050

journalctl shows (grepping just gdm):

Jul 13 14:30:44 haz gdm-launch-environment][1051]: pam_unix(gdm-launch-environment:session): session opened for user gdm by (uid=0)
Jul 13 14:30:44 haz systemd[1]: Created slice User Slice of gdm.
Jul 13 14:30:44 haz systemd-logind[905]: New session c1 of user gdm.
Jul 13 14:30:44 haz systemd[1]: Started Session c1 of user gdm.
Jul 13 14:30:44 haz systemd[1061]: pam_unix(systemd-user:session): session opened for user gdm by (uid=0)
Jul 13 14:30:46 haz gnome-shell[1089]: JS WARNING: [resource:///org/gnome/shell/gdm/util.js 331]: reference to undefined property this._preemptingService
Jul 13 14:31:15 haz gdm-password][1429]: pam_unix(gdm-password:session): session opened for user dan by (uid=0)
Jul 13 14:31:15 haz gdm3[1046]: Cannot find a command for specified session: ubuntu-wayland
Jul 13 14:31:15 haz systemd[1]: gdm.service: Main process exited, code=exited, status=1/FAILURE
Jul 13 14:31:15 haz systemd[1]: gdm.service: Unit entered failed state.
Jul 13 14:31:15 haz systemd[1]: gdm.service: Triggering OnFailure= dependencies.
Jul 13 14:31:15 haz systemd[1]: gdm.service: Failed with result 'exit-code'.
Jul 13 14:31:16 haz systemd[1]: gdm.service: Service hold-off time over, scheduling restart.
Jul 13 14:31:16 haz gdm-launch-environment][1517]: pam_unix(gdm-launch-environment:session): session opened for user gdm by (uid=0)
Jul 13 14:31:16 haz systemd-logind[905]: New session c2 of user gdm.
Jul 13 14:31:16 haz systemd[1]: Started Session c2 of user gdm.