There are Cirrus Runners which is a service of managed GitHub Actions Runners powered by M2 chips. But there is no free option for OSS yet. https://tart.run/integrations/github-actions
This one is ridiculous. This should already exist. Until GitHub builds it, you can use GitHub Actions to kick your builds off but run them remotely on Earthly Cloud (https://earthly.dev/). Even the free tier includes arm64 remote runners.
Note: I work at Earthly, but I'm not wrong about this being a good, free, arm64-native workflow for GitHub Actions.