if it's useful, they do actually have arm workers now for linux and mac: https://github.com/actions/runner-images/tree/main?tab=readm...

TIL amd64 is also called x86-64.

They have these now.

Only for public repos though - if you're in an org with private repositories you don't get access to them (yet).

You do, you just have to set them up at the organization level. Windows/Linux/macOS are all available.