It was back in May that the surprising event happened of AMD posting HDMI 2.1 FRL patches for their open-source AMDGPU Linux driver as part of their broader HDMI 2.1 bring-up.
For years the open-source HDMI 2.1 support in AMDGPU was blocked by the HDMI Forum but whether it was due to Valve or some other event, the code was finally unblocked.
While it's been part of the kernel since Linux 7.2, it's been disabled by default -- except that is now changing...