Which display manager is used by default in Ubuntu GNOME 16.04?
I can't find this information, and while trying to install the nvidia drivers for my laptop, I got a message explaining that I had 2 display managers installed, and that seemed strange.
Ubuntu GNOME uses GDM as its default display manager.
This can be verified by looking at the dependencies for the ubuntu-gnome-desktop package, which include gdm3 but not lightdm.
http://packages.ubuntu.com/xenial/ubuntu-gnome-desktop