I’m honestly just curious how they managed to get a KVM based solution working on MacOS ARM64. Buildah and few other dependencies appeared to be Linux only... but the brew install worked..
The key is that libkrun (https://github.com/containers/libkrun), the library that krunvm uses for running the VMs, as recently integrated support for Hypervisor.framework on ARM64, in addition to KVM.
As for buildah, the Homebrew repo contains a build that includes this PR (https://github.com/containers/storage/pull/811).