systemd-firstboot.service hanging at first boot

The systemd-firstboot.service job hangs at first boot, preventing any other systemd services to start.

A workaround is to cancel it by running systemctl cancel "$(systemctl list-jobs | grep systemd-firstboot.service | awk '{print $1}')". This is automatically done by the first-setup script when running the image for the first time.

The actual root cause of this issue (and the eventual proper fix for it) is not known yet.