I owned MBP M1 Max this summer. I already have an MBP M1 and the monitor that I've been working with for several years without any issues. But I was offered to purchase a used MBP M1 Max 2 / 64 at a good price, so I did. When I connected it to my monitor, I couldn't work. Stillcolor disabled dithering, but there was something else in the signal. Reflashing the Mac in DFU mode to different versions of Sonoma and Ventura didn't help. I ended up reselling it.
It's hard to say if anything can be done without analyzing the video signal from such devices. Since temporal dithering should be turned off via Stillcolor (here I'm talking about an external monitor without FRC), I don't know what else might be in the signal of such problematic Macs.