BLAS/LAPACK isn't that much of an issue, since Apple probably will need to ship their own implementation of this for Apple Silicon to get reasonable performance, and they can implement this in C, assembly, or whatever they want.

If they don't do that, then you can just use any "generic" C BLAS/LAPACK implementation, performance will be poor, but that's pretty much the only option if your hardware vendor doesn't support BLAS.

I guess people can write their own BLAS as well, but if you want to re-implement BLAS in 2020, then Fortran is probably not the best language to do that.