[B] If you want your GitHub Enterprise Server instance to use third-party custom actions, you need to enable GitHub Connect.
[C] Most official GitHub-authored actions are automatically bundled with GitHub Enterprise Server, and are captured at a point in time from GitHub Marketplace.
[F] Third-party actions can be manually synchronized to GitHub Enterprise Server (GHES) to be used in workflows without requiring an internet connection to GitHub.com. This is done using the actions-sync tool to download actions from GitHub.com and transfer them to the GHES instance.
This manual method provides an alternative to using GitHub Connect, offering stricter control over which actions are available on the GHES instance.
Reference:
https://docs.github.com/en/[email protected]/get-started/exploring-integrations/about- using-integrations
https://docs.github.com/en/[email protected]/admin/managing-github-actions-for-your- enterprise/managing-access-to-actions-from-githubcom/about-using-actions-in-your-enterprise

The check_run event is triggered when a check (such as a code quality check) completes, including when the status of a check changes. By adding this event as a trigger, you can initiate a follow-up workflow when the code quality integration finishes its checks.
Reference:
https://docs.github.com/en/actions/reference/workflows-and-actions/events-that-trigger-workflows

Using GitHub Actions with an IP allow list. If you use an IP allow list and would also like to use GitHub Actions, you must use self-hosted runners or GitHub-hosted larger runners with static IP address ranges To allow your self-hosted or larger hosted runners to communicate with GitHub, add the IP address or IP address range of your runners to the IP allow list that you have configured for your enterprise.
Reference:
https://docs.github.com/en/enterprise-cloud@latest/organizations/keeping-your-organization- secure/managing-security-settings-for-your-organization/managing-allowed-ip-addresses-for- your-organization

GITHUB_REF : The branch or tag ref that triggered the workflow.
Reference:
https://graphite.dev/guides/github-actions-variables

The enterprise Actions policy is the centralized place where enterprise owners enforce which actions and reusable workflows are permitted across all organizations in GitHub Enterprise Cloud. From this scope you can require that only actions and reusable workflows hosted within the enterprise are allowed to run, and this policy flows down to organizations and repositories to ensure consistent enforcement.