Hi,
I managed to hack PyValhalla to run a Mac os arm valhalla build I made a week or so ago
Once the isochrone issues I encountered are sorted, I should be able to help out with the build process for PyValhalla
Can't say I know exactly what is going on in the build scripts here, but to me it looks like the main thing to change from "build_mac.sh" would be pathing to the mac os arm location