Yup, I wonder if that's HDMI Forum's fault though. I hear they are insufferable.

There are all sorts of licensing shenanigans when dealing with HDMI, so I wonder if it's compatible with their open source policy. But personally I'd have put a VGA output on it as a compromise between period correctness and modern usage. Easy to output as analog from the console, and easy to convert cleanly for modern displays with inexpensive adapters.