A long-awaited feature is now available on GitHub: share actions in your workflows in your enterprise from Internal Repositories 🤖 !
Until today, Actions had to be stored in a public repository, to allow other repositories to use them in workflows (or take a complex approach). This has changed 🎉.
Now you can put your actions in an internal repository; repositories visible to your whole enterprise.
Once your repository visibility is set to "Internal", in the Settings pages, click in the Actions section and select the proper Access configuration:
The following video shows this feature in action: