So I installed gnome-session, but I can't select it, since the Gear Icon in the Login screen of Ubuntu 18.10 is missing... Anyone knows a solution to this? Thanks!
https://www.gnome.org/getting-gnome/ "Ubuntu 18.10 includes GNOME 3.30 with minor alterations. If you install gnome-session, you can also choose to launch a pristine GNOME from the login screen."