Following AMD completing their HDMI 2.1 implementation for the open-source AMDGPU Linux driver after beginning with HDMI FRL patches earlier in the year, Intel's open-source driver developers are following in their footsteps.
Back in August, Intel began posting patches for HDMI 2.1 FRL for Intel Meteor Lake and newer graphics. HDMI Fixed Rate Link of the HDMI 2.1 spec is needed for supporting higher resolutions and refresh rates with today's high-end displays. After two months of silence, the second iteration of those patches were posted today.
Intel engineer Ankit Nautiyal posted the v2 patches that addressed prior review comments, pipe joiner support for HDMI being enabled, audio prune is added for the HDMI FRL usage, and various other tweaks. These new patches for HDMI FRL have also now been lightly tested on Intel Panther Lake hardware with 4K@120 being among the modes now working. Though 8K outputs with Panther Lake aren't yet supported due to the Display Stream Compression (DSC) not yet being wired up.
With these latest patches, they are still marked as a "work in progress" with the overall design still being finalized and reviewed. Long story short, these patches aren't yet near a stage for merging and thus likely won't be until at least into 2027 before this HDMI 2.1 FRL support for modern Intel graphics hardware is in the mainline Linux kernel.
In any case those wanting to test out the HDMI 2.1 FRL support for Intel Meteor Lake and newer hardware can find the updated patches on the dri-devel mailing list.