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.
3Thanks, so this is nvidia-prime which depends on lightdm and force-install it Jun 20, 2016 at 12:46
2Yes, nvidia-prime not recognizing gdm3 is a bug. It's an easy fix so hopefully it will be fixed for Ubuntu GNOME 16.04 LTS before long. Jun 28, 2016 at 22:18
Nick, please include the nvidia information in your answer to make it even better Oct 23, 2016 at 9:46
@RamonSuarez If you'd like to include that information in my answer, please feel free to edit it. Oct 23, 2016 at 12:17
This answer is confusing. gdm != gdm3. Which is the default?– CerinNov 20, 2016 at 21:26