GDM display server

I notice some people with Nvidia cards are having problems getting any display in Ubuntu 17.10, what display server does GDM use by default?

So far, I’ve seen only the usual churn of users with almost-but-not-quite compatible video cards.
Always a spike in those around release time.
Many forgot that they changed kernel modules long ago to fix the problem, and just re-installed afresh.

As I help them, I gently remind them they might want to write down this process for the next time they reinstall on this hardware.

If you discover signal among the noise (real trends), like the wiki instructions don’t work anymore for certain models, or certain models that stop working after an otherwise successful upgrade, those would be good to know.