I did this but with a dedicated machine for the Silicon Motion sm750 GPU. A budget single HDMI output GPU card for servers and a max resolution of 1080p. It is based on an older VGA/DVI version of the same hardware.

I'm still testing but oh wow. My new driver now works with my ultra wide 21:9 ratio at 2048x864, it also manages 2048x1152.

The driver works well, and now has full DRM and DKMS support. It also runs on modern Linux after the manufacturer decided only to go up to kernel 5.x, windows support obviously still fine.

It found many faults in the original source, like somebody didn't read the HDMI specs / didn't have any idea what they were doing.

The new driver is fully spec timings and sequence compliant, doesn't hang on shutdown anymore, and ignores EDID for the purpose of allowing more screen modes.

It also has double buffering, and shadow buffering, and a custom magic square dither mode for 16bit colour and it absolutely flies vs the 32bit mode. The dither I invented was derived from one I created years ago for some retro hardware, but it's so good it's (imho) indistinguishable from general jpeg artifacting and quite difficult to find/see. I've had to ask codex a few times to check the GPU isn't in 32bit colour.

The GPU still has an annoying bug and won't work over KVM consistently without losing sync in VESA modes, but I'm not convinced its the GPU hardware doing this, it works perfectly well directly connected.

I'm due to put a GitHub repo up for this as soon as it's battle tested, and obviously ensuring it uses EDID by default, rather than ignores it.

I'm hoping somebody can fix the KVM issue, or audits the source to confirm there's nothing that can be done, but that's the best thing about open source :)