enabling the built in color profile desaturates colors quite a bit and does some kind of perceived brightness to luminosity mapping that desaturates bright / dark hdr content even more

It maps the colors to be more correct, and it does use the brightness info from the EDID for HDR content, so that checks out.

I think there must be something wrong with my screen since the hdr reduces saturation more than anything else

It might enable some sort of gamut mapping on the display side… HDR on monitors is really weird sometimes.

Side note, when I turn off hdr only from kscreendoctor the display stays in hdr mode until it turns off and on again, that didn’t happen with nvidia

I think that’s a bug in amdgpu. It should force a modeset on hdr change, but it doesn’t.