You can just buy a dongle online that does this. It’s an HDMI dongle that tells the OS that you have a monitor plugged in when you don’t. There is a way to make the adapter yourself (paperclip hack), but using an actual adapter has the advantage is it can support higher resolutions that you can then export over VNC.
Seems like if it’s not loading the driver then it should be possible to just load it with kextload? No? I can’t imagine that it’s not a module if it gets activated later, but obviously I could be wrong. I’m not a MacOS kernel hacker.
I guess that would be easy to check by running kextstat before and after plugging in the DisplayPort.
Sadly I only have a 2013 Mac Pro (which has AMD graphics only) so it will operate differently. :/
Paperclip hack is the resistor hack that others in the reply have linked to. My paperclip has been in situ for a few years so don't have the original source, but one of the resistor hack how to postings suggested that there was enough resistance in a paperclip and had a spare display adapter kicking around so tried it and it worked for me. Laggy performance on headless Mini ended.
