Serial port or serial port over "ethernet"[1] (technically it's 8p8c[2]).
My router doesn't have a video port, but it does have a dummy terminal port. I had to scrounge a video card for my server to set it up, but it does have a serial port [3]. So that would have been nice.
Also would be nice for a modern remake of dumb terminal with abandoned monitors.
I've looked into it with a PiZero and some HATs but I'd like something made by smarter people. This would be perfect for that.
Ideally just some dip-switchs to set the terminal to emulate and set the display resolution.