if you're savvy enough to know about gdm, you're savvy enough to know to include at least some details, like what graphics you're running, X11/Wayland, etc.

UPDATE: Resolved, it was an issue caused by a faulty display port cable. Different issues from this cable had happened recently, I just initially assumed it was a software issue due to the fact that only GDM was affected.

Last time I had a similar-ish issue it was some graphic card drivers failing. Ones I didn't even need nor could use but somehow ended installed. Check the log from the boot sequance. Generally its Linux - you'll find answers in some log.

Or just purge and reinstall GDM. (your expiriance may vary)

I'm not up to speed on GNOME, not a fan of it, but can't you just try a different DM? like SDDM? would that work? seems silly that GNOME would lock you into their DM.

Have you tried booting from an older kernel? When I was on Fedora I had things like this happen from time to time and would always go back to one of the archived kernels and wait for another update.