OpenBLAS can now be built for Apple chips using the port at https://github.com/iains/gcc-darwin-arm64.
The build succeeds and seems to run fine, so it might be time to think about tuning for this microarchitecture.
If anybody is interested in working on this issue, I can probably facilitate hardware access.