Earlier quoted context omitted.
I don't want to argue on semantics. Currently you can't start a graphical session completely remotely using any protocol (RDP, VNC, no machine, whatever).
I don't use GNOME, or GDM, or RDP, but isn't https://gitlab.gnome.org/GNOME/gnome-remote-desktop#headless... describing that? > GNOME Remote Desktop supports integrating with the GNOME Display Manager (GDM) to achieve remote login functionality. This feature is only available via the RDP protocol. It works by the remote user first authenticating via a system wide password, which gives access to the graphical login sc…
Please do.
I've seen too many threads like this based on a hunch and docs, while it just doesn't work.
I'll be more than happy to be proven wrong.