Workstation GPUs (Nvidia Quadro[1][2] / AMD Radeon Pro[3]) can emulate/force an EDID in the driver settings and the OS will "think" a display is attached. At least in theory that should get around the handshake.

[1] https://www.nvidia.com/content/Control-Panel-Help/vLatest/en...

[2] https://nvidia.custhelp.com/app/answers/detail/a_id/3569/~/m...

[3] https://portal.7thsense.one/user-guides/MC264-display-config...