Error: CRuby < 2.6 does not support macos-arm64. Either use a newer Ruby version or use a macOS image running on amd64, e.g., macos-13. Note that GitHub changed the meaning of macos-latest from macos-12 (amd64) to macos-14 (arm64): https://github.blog/changelog/2024-04-01-macos-14-sonoma-is-generally-available-and-the-latest-macos-runner-image/ If you are using a matrix of Ruby versions, a good solution is to run only < 2.6 on amd64, like so: matrix: ruby: ['2.4', '2.5', '2.6', '2.7', '3.0', '3.1', '3.2', '3.3'] os: [ ubuntu-latest, macos-latest ] # CRuby < 2.6 does not support macos-arm64, so test those on amd64 instead exclude: - { os: macos-latest, ruby: '2.4' } - { os: macos-latest, ruby: '2.5' } include: - { os: macos-13, ruby: '2.4' } - { os: macos-13, ruby: '2.5' } But of course you should consider dropping support for these long-EOL Rubies, which cannot even be built on recent macOS machines. at validateRubyEngineAndVersion (/Users/runner/work/_actions/ruby/setup-ruby/v1/dist/index.js:65892:11) at setupRuby (/Users/runner/work/_actions/ruby/setup-ruby/v1/dist/index.js:65784:15) at run (/Users/runner/work/_actions/ruby/setup-ruby/v1/dist/index.js:65743:11) at /Users/runner/work/_actions/ruby/setup-ruby/v1/dist/index.js:65942:40 at /Users/runner/work/_actions/ruby/setup-ruby/v1/dist/index.js:65944:3 at Object.<anonymous> (/Users/runner/work/_actions/ruby/setup-ruby/v1/dist/index.js:65947:12) at Module._compile (node:internal/modules/cjs/loader:1469:14) at Module._extensions..js (node:internal/modules/cjs/loader:1548:10) at Module.load (node:internal/modules/cjs/loader:1288:32) at Module._load (node:internal/modules/cjs/loader:1104:12)