What is the state of Nvidia and AMD GPU drivers on Linux? Maybe these techniques can finally give us reasonably good open source drivers which can be supported for a long time.

AFAIK Nvidia drivers are proprietary and AMD has a tendency to drop support quickly

AMD driver support is great due to community effort, even for 10+ year old cards. Nvidia also now has (partly?) open drivers.

amen to that. amdgpu is a shitshow for years. im sure the firmware plays its part in the shitshow, but amdgpu does as well.