That said, are you talking about a full graphics stack, or just the GPU-specific bits? Modern Linux graphics heavily emphasize code reuse across architectures, both on the kernel side and userspace side, which is completely different from how vendors typically do things.

The goalposts are quite different between having a fully compliant implementation that can deal with software that uses the GPU intensively (and hits all the corner cases properly), which is what Apple has to build, and being a usable desktop experience for Linux - having the whole stack be open source makes debugging things a lot easier too. Getting to full Vulkan compliance is definitely not going to be a one-person job. But we've seen fairly fast progress on GPU drivers going from triangles on the screen to simple game ports in some cases, with only one or two developers involved. I obviously don't have any yardstick for how the Apple GPU compares to everything else, but a priori, my hope is to be able to push things past the initial cliff to where the GPU starts being useful, and then of course other contributors can help improve support. In my experience, the initial hurdle in building a community project is often the hardest part, as a lot of people have no idea where to start supporting undocumented hardware (and I'm particularly good at doing black-box reverse engineering of this kind of stuff; I can claim a good 15 years+ of experience there myself). For example, once e.g. the shader ISA is documented and a PoC backend implemented, I expect people with more shader optimization experience than me to want to pitch in and make it faster.

Re firmware, I would expect to use Apple's (at least initially).