This is the best summary I could come up with:

If you were hoping at some point to see HDMI 2.1+ on Linux with AMD + Mesa, you're out of luck right now as it's simply not going to be happening.

There's been a bug report on the Mesa GitLab of "4k@120hz unavailable via HDMI 2.1" that's been open for a few years now, with lots of comments and chatter about the issue.

In an update on the bug report, AMD engineer Alex Deucher commented: "The HDMI Forum has rejected our proposal unfortunately.

So if you're on Linux, it's going to continue to be best to buy hardware that uses DisplayPort.

On the NVIDIA side though, it seems like it may not be an issue, as developer Karol Herbst wrote on Mastodon: "Even though AMD might not be able to add support for HDMI 2.1, nouveau certainly will as Nvidia's open source driver also supports HDMI 2.1 so there is no reason to believe that at least some drivers can't support HDMI 2.1

It's quite backwards, but apparently having all the logic inside firmware (like Nvidia does) will probably help us implementing support for HDMI 2.1"

The original article contains 244 words, the summary contains 183 words. Saved 25%. I'm a bot and I'm open source!