When you click on the gear icon on the GDM login screen, it provides a list of the available desktop environments so you can pick between them.
Since I exclusively use Mate on this computer, how can I remove the other options from that menu? Earlier today when I logged in the machine decided on its own that what I really wanted was Gnome Classic, so I had to log out to change it back to Mate, then log in again.
I would like to tell it to use Mate exclusively, with no other options to select by mistake.