Funnily enough, this is exactly what I was talking about. Nvidia supported multiple monitors on Linux for decades using TwinView, they simply didn't add support for the open source xrandr for 4-5 years, but even that has been supported for ~7 years now.

> Nvidia supported multiple monitors on Linux for decades using TwinView

And Xorg supported them for decades before using Xinerama. Instead of collaborating with upstream, they just dumped something incompatible and broken, and said "Deal with it".

Multi monitor display worked perfectly for long time, long before "it works on intel, let's call it new standard" crew decided that flat shared framebuffer is the only way to go (apparently because of compositors and nothing else), something that also broke support for multi-gpu and especially heterogenous multi-gpu.

Zaphod mode is still available. nVidia pushed its TwinView solution while everybody else was using either the Zaphod mode or Xinerama. I don't think TwinView on Linux allowed any dynamic configuration. So, when the rest of the world switched to the RandR extension, every graphic card was able to dynamically add/remove monitors while nVidia users were stuck with a subpar solution.