I have a reference AMD RX6800 GPU and recently bought a USB-C to HDMI 2.1 adapter from Cable Matters ( https://www.cablematters.com/pc-1368-125-48gbps-usb-c-adapter-supporting-8k-video.aspx ).
It works fine at 3840x2160 @ 120Hz at 10bit though my display supports up to 12bit. Via a normal HDMI 2.1 connection 12bit is available but not with the adapter.
After talking to Cable Matters support and them confirming that 12bit output works on an Nvidia card with USB-C out. And it not working on my RX6800 no matter what resolution and refresh rate I choose (with 1280x720 @ 30Hz it still doesn't show up) I am now here to ask the question of the title.
I have already cleaned and updated my driver to the latest version with no change. And have been through everything the Cable Matters support and I could think off with no change.
