Backport of df3e92ff96 https://github.com/NixOS/nix/pull/11009 GitHub Actions seems to have magically switched architectures without changing their identifiers. See 2813ee66cb/README.md (available-images) Maybe they have more complete documentation elsewhere, but it seems to be incapable of selecting a runner based on architecture.
df3e92ff96
2813ee66cb/README.md (available-images)