A little update on this.
- After massive internet search I managed to get
zinkworking by switching fromxf86-video-amdgputo embedded modesetting driver inxorg.conf amdgpuappears to have parameterdeep_color, defaulted to… right, 0. So one needs to add a line tomodprobe.d(in caseamdgpuis loaded as a module) or addamdgpu.deep_color=1to the kernel command line (if embedded).
At the moment I can’t investigate it further due to the lack of time, but it seems that 10-bit output is an achievable target.