I am also unhappy to confirm this problem but happy to find that this is a corroborated bug. As the OP reports, "gdm3" hangs the system before the Unity desktop comes up, and trying to use "sddm" starts an X session without any window management.
I am also unhappy to confirm this problem but happy to find that this is a corroborated bug. As the OP reports, "gdm3" hangs the system before the Unity desktop comes up, and trying to use "sddm" starts an X session without any window management.