"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 🙃"