It's bugs on bugs, with bugs chasing bugs! So little developers, so complex stack with 25 years of technical debt, and little community around because it's not a sexy technology to be involved in.
That's why I have to dive deep and fix my bugs myself if I want to make it work properly as I would like it to. I also ended up making my own print server device, because China did not make a proper one for some reason for all these years.
The last time I checked (a year ago), 1bpp was suddenly supported only by Windows. IIRC, monochrome is REQUIRED, while bi-level is OPTIONAL in RFC.
Not sure how things stand now, though. Ever since then, I've just been carrying Floyd–Steinberg dithering around.