Comment 1 for bug 1790478

I have found this to be locally reproducible with:
$ autopkgtest --shell-fail --apt-upgrade --no-built-binaries --testname=boot-and-services --apt-pocket=proposed=src:systemd,src:dbus,src:iproute2,src:glibc systemd_239-7ubuntu6.dsc -- qemu --qemu-options='-cpu host' --qemu-command=qemu-system-i386 --cpus 8 --ram-size=4096 ~/autopkgtest-cosmic-i386.img

What I see is that it really is failing.
There are plenty of crashes in journal but those seem to be a swarm of red herring.

The first start of gdm ends with X11 initializing and giving up like:
/usr/lib/gdm3/gdm-x-session[pid]: dbus-daemon[1112]: [session uid=119 pid=1112] Activating service name='org.freedesktop.systemd1' requested by ':1.0' (uid=119 pid=1053 comm="/usr/lib/gdm3/gdm-x-session gnome-session --autost" label="unconfined")
/usr/lib/gdm3/gdm-x-session[pid]: dbus-daemon[1112]: [session uid=119 pid=1112] Activated service 'org.freedesktop.systemd1' failed: Process org.freedesktop.systemd1 exited with status 1
/usr/lib/gdm3/gdm-x-session[pid]: Unable to register display with display manager

But if you log in later and run "systemctl restart gdm" then all initializes as it is supposed to.
It seems something yet unknown isn't available at early boot.

I compared the X11 init of good/bad case but there is no difference (e.g. in detected HW), the first things that fails/differs is the org.freedesktop.systemd1 activation.

But the boot start of gdm seems to be really (too early?) as halfway through I see:
  "Reached target Basic System"