Multiseat Setup: Disable display manager and use TTY on one seat

I have the following setup (HP Microserver 8): - Integrated Matrox G200eH connected to Integrated Lights Out (the PH Remote Management Console) which also simulates an integrated keyboard to the system - Dedicated NVidia Quadro P400 GPU which is intended to be used for X applications via VNC/remove X-sessions When originally setting this up with all devices on seat0, I noticed that the integrated GPU didn't show the TTY anymore as the dedicated GPU has taken over the master (and the keyboard can now used within the Display Session) I'm now trying to set up a separate seat1 which only includes the dedicated GPU, while seat0 will control the integrated GPU + keyboard via TTY. Unfortunately I haven't managed with any display manager to limit startup of the display manager and X to seat1, so seat0 can still be used for remote administration via CLI. I tried both lightdm as well as gdm3 with no success (you can't exclude seats in either), and I couldn't find a way to use TTY as a greeter either. Is this something I can do by removing the master-of-seat tag via udev from the matrox card?