Summery: The AMDGPU Driver forces to YCbCr, but your Monitor works with RGB. It is an Upstream problem, since there is not smart switch to force to RGB. Although Windows has it in its driver. Solution is to get the EDID of your screen, modify it (disable YCbCr) and use the modified EDID for the driver.
OR simply use DisplayPort instead of HDMI (I guess only HDMI is the probematic connection here).