Comment 21 for bug 1500673

Can anyone still affected by this please attach the output of `journalctl`. Saying that your system boots to a blank screen is not particularly helpful, there there could be numerous reasons causing that, such as hardware specific driver bugs, dependency issues etc.

The recommended way to run GNOME desktop is to install:
sudo apt-get install ubuntu-gnome-desktop^
While installing the bits and pieces standalone should work, it doesnt get anywhere near as much testing as the complete packageset above.

re Wayland comments:
The gdm wayland greeter is not available by default and gdm automatically falls back to the X backend in this case (so no need to mess with custom.conf here). if you want to use gdm wayland or just wayland in general you must install: gnome-session-wayland , xwayland by itself is not enough.

ubuntu-gnome-default-settings:
I have no idea why this package being missing would affect gdm. Though if it is indeed the schema overrides that fixes it perhaps it is caused by the ubuntu overlay scrollbars or otherwise one of the default settings points to a missing file/font perhaps.
This package is pulled in by default when using ubuntu-gnome-desktop