I read that Canonical didn't like having to fiddle with lightdm to make it work and play well with GNOME shell, and thus Ubuntu 17.10 comes with gdm3. My upgrade went south, so I installed Kubuntu. It's using sddm, which I understand is the successor to kdm. Now I find that Gnome under X just hangs. Does GNOME shell require either gdm or something hacked as Canonical did lightdm to work?