Comment 27 for bug 1705369

Tried again, this time remembering to tell my BIOS not to auto-disable the integrated graphics, so now I have both:

$ ls /dev/dri
by-path card0 card1 renderD128 renderD129

But the outcome is the same. GDM and gnome-shell work perfectly with only the Nvidia card plugged in. They just allow Xorg sessions and hide the Wayland options.

So it seems the relevant smarts are working in gdm. I'm not sure what's different about your machine other than the card model.