Translations:GNOME/GDM/25/en

GDM produces an all-black screen when more than one video driver is loaded
One of the benefits of Wayland is the ability to run multi-GPU multi-head sessions. It is also possible on some compositors (e.g. Sway) for users to do this with multiple GPU drivers (e.g. running a modern AMDGPU card and an older radeon card in the same machine). GDM is not a fan of this, but it can be coerced into behaving.