The "fix" would be to make games perform like shit on Windows and disable HDR and other proprietary features, or to abolish the open Linux drivers. You can't have both, unless you do what Nvidia does and move all of the proprietary stuff to the GPU firmware and write a minimal driver to control that massive firmware blob. Which, obviously, would require reengineering the GPU hardware, which is expensive and of questionable value.

They can't open source their proprietary drivers even if they wanted to because they don't own all of the IP and their code is full of NDA'd trade secrets. AMD isn't paying two different teams to do the same work because they like wasting money.

I guess that you don't understand that how silicon and 3rd party IP works. It took Intel a completely new GPU from scratch to be able to open drivers. AMD did at least one revision to their silicon to enable that kind of openness.

Yet, HDMI forum said that they can't implement an HDMI2.1 capable driver in the open, with some nasty legal letters.

I have a couple of friends who wrote 3D engines from scratch and debugged graphics drivers for their engines for a living. It's a completely different jungle filled with completely different beasts.

I think being able to call glxinfo on an AMD card running with completely open drivers and being able to see extensions from NVIDIA, AMD, SGI, IBM and others is a big win already.