This would require support in cibuildwheel: pypa/cibuildwheel#473

We will need NumPy wheels too, I think: numpy/numpy#18143

Pillow has arm64 wheel, thought not universal2. We will also need kiwisolver wheels: MacPython/kiwisolver-wheels#13

These have been built for 3.5.0rc1. Can someone check whether the arm64 and universal2 wheels work on Apple Silicon? And that the universal2 wheel works on x86_64 as well?

The 3.5 release contains the universal2 wheels now. I can confirm that installing the universal2 on x86_64 works for me locally. I can't test on Apple Silicon, but I think we can close this for now and if people have issues we can reopen.

Why are Universal2 wheels no longer available after version 9.0.1? I need a Universal2 wheel for my application to support a universal binary. Can you provide guidance or alternatives?

See #26125 and numpy/numpy#20787 (comment). There is no 9.0.1 version of Matplotlib; universal2 wheels were removed in 3.8.0.

Do you know a work arround to still build an universal application?

See instructions in numpy/numpy#20787 (comment) for how to generate the fused wheels if you need them.