Somehow I did not come across this when researching existing solutions. Looks interesting though, I'll look into it

Yeah, I immediatly thought of this. They even have pre-built images.

I wonder what OP uses as a DE. In sway (and presumably other wlroots-based compositors) it's very easy (one command) to add a headless output.

Edit, as I saw your username: sadly it's undocumented in the man page, IIRC :P