In order to muck around with video to make a Pi look like an Archimedes adffs needs EDID turned off in config.txt
Since my monitor is an old DVI single-mode flatscreen this was complicated. I'd wrestled with this monitor and the Pi0 when I was trying to get an HDMI sound box to work and it defeated me.
This time I win! EDID is ignored, monitor is getting fed the mode it likes, adffs is happy, so I can play Star Trek!
"I appreciate SDF but it's a general-purpose server and the name doesn't make it obvious that it's about art." - Eugen Rochko