GitHub Actions and Enterprise 3.0

With the introduction of actions in GitHub Enterprise 3.0, is there an ability to create and publish actions only within say an enterprise marketplace and not to the public marketplace?

No, that is not possible.

Hmm, that takes away the ability to write organizational specific logic. That is quite disappointing when I’d like to sunset usage of Jenkins and go GitHub native.

The marketplace is just a list of Actions, it doesn’t introduce any additional functionality and isn’t a dependency of creating / using / distributing Actions: the Actions themselves are referenced through a GitHub Repository, meaning you can have private organisation Actions.

The native implementation of private repository support for Actions is still on the GitHub Roadmap but there are a number of ways to achieve it yourself, e.g: daspn/private-actions-checkout, nick-invision/private-action-loader or with submodules or even the documented approach of using actions/checkout.