It was recently developed why FreeSync media via HDMI does not come to open-source drivers, at least not yet … It results from the HDMI Forum’s decision to prevent public access to HDMI specifications, which in turn harms open-source graphics drivers.
The HDMI specification is no longer public, but only for “HDMI Adapters” complicates support for the open source GPU driver. Even for those who are part of the HDMI Forum, such as AMD, in turn, can not provide an open-source implementation of the features covered by the closed specifications to open, in turn, potentially and indirectly, its aspects to public.
This seems to be the main blocker for why FreeSync with the open-source Linux AMDGPU kernel driver works only with DisplayPort connections and not HDMI, which has consistently been one of the main questions regarding FreeSync Linux support and its current shortcomings. .
The current restrictions on the HDMI specifications jeopardize a lot of advanced HDMI functionality so that HDMI 2.1 is not implemented in open-source graphics drivers.
The X.Org Foundation requires the HDMI Forum to allow at least some information about HDMI 2.1 specifications to be publicly disclosed so that open-source graphics drivers can implement (legally) functionality.
Hopefully this will work in 2021 … In the meantime, keep this in mind when deciding your DisplayPort Vs. HDMI!