From what I’ve seen, a lot of 90s driver work was exactly that mix of partial docs, trial-and-error with registers, and mailing some engineer at the card vendor hoping they’d admit to a bug. It wasn’t glamorous, but it’s kind of wild how much of it came down to persistence and a bit of luck

Thanks. I bet there were a lot of battle stories like what I read. Alas most of those went into history's garbage bin :/

I was even thinking about getting my hand on a few cheap physical cards (not sure which ones are cheaper), a Pentium box, and see if I can do anything -- even displaying some colors is fun enough.