How is GPU support going?
It means that right now there is no GPU support on Linux, but once the kernel driver (which is simpler than the userspace part) is written, things will go from nothing to likely able to run a full accelerated desktop in days, since the bulk of the userspace work will already be done.
I'm working on the display controller driver first (since it is arguably more complex in interface, but shares concepts, and is also a dependency for "real" GPU acceleration since you need things like vsync/page flipping to do it properly), and once that's able to at least do basic screen bring-up, I'll tackle the GPU side.
https://rosenzweig.io/blog/asahi-gpu-part-4.html
At the launch there were various pronouncements that "it'll never happen, Apple will have locked it down so hard it'll never go anywhere" and the more optimistic "there should be a start in a couple years" and at this point I wouldn't be surprised if there was something alpha or pre-alpha grade that you can toy around with by the end of the year (my words not hers - I have no relation to any of the Asahi Linux efforts).
Once that one is merged there's already another series to enable PCIe (which needs the iommu driver) which gives us more USB ports, ethernet and with another small patch WiFi. There's also a WIP series for NVMe.
What's missing are then a few smaller things (i2c, spi, keyboard on the macbooks etc.).
And then there are a few bigger tasks left, e.g. thunderbolt support, usb super speed support, support for the secure enclave, and ofc the largest one being the display controller and the GPU.
And once that's all done there's the long tail of making this all work nicely (e.g. power management, making the installation as easy as possible, etc.)
Personally, I'll consider the project at success if we can match or exceed the features and stability of an average x86 laptop running Linux, with the performance and power efficiency advantages that Apple Silicon brings, which I think is totally possible.