WhisperingWind oh interesting so turning it off on driver side at least will prevent os dithering. Lubuntu does sound promising. I did try HiveOS when I use to mine crypto and the desktop booting felt comfortable when I tried it on a amd igpu. I think lubuntu is similar with using open box/x11. I think lubuntu has the compositor disabled default right ? Assuming that would be better ? WhisperingWind Ahh okay. Tbh it might be more trouble than it's worth. I probably would just find a 2018 Mac mini in that case but I think for now I'll try the hardware I currently got.
I emailed the vpixx/psychtool box company and they told me they personally use the Rx 6600 with ubuntu but they said it requires this tool: https://gitlab.freedesktop.org/tomstdenis/umr to disable dithering.
They also gave me a method on example code for checking dithering with a frame grabber but videodiff I think already exists for that on GitHub.