Using my NVIDIA GTX 750 via HDMI (VGA for the Intel chip) gdm loads and gnome is using Wayland!
I uninstalled xf86-video-nouveau and it still works. The performance is inferior to the proprietary driver (tested using google map’s satellite view), but there is no tearing!
The speckled grey background is gdm’s background, so it’s just not loading the login entry (or anything other than the background) using the Intel graphics chip. I wonder if the problem is VGA (the only option) or that it’s an older intel chip.