GitHub Actions debugging tip: You can connect to the running build with ssh and get a shell within the GitHub Actions runner VM.
The recommended approach is to run the build in a PR in your own fork and make only temporary changes to enable the ssh shell. GitHub Actions runs within your own fork when you open a PR to your own fork. Before opening the PR, it's useful to sync your fork's master branch with origin/master. Please check instructions for "Personal GitHub Actions CI" in the dev mailing list archives.
Here's an example of SSH debugging I have: lhotari/pulsar-helm-chart#1 . I removed all other GitHub Actions workflows and added this action step to the workflow where I wanted to connect with ssh:
- name: Setup upterm session