Apple also offers unlisted app distribution. You can read all about this in this article from Apple:

Pre-requisites for unlisted app distribution:

  • Your app must either already have a live version the public App Store, or be ready for final distribution and submitted into review with Apple.
  • You must add a note in your app's Review Notes that the app is intended for unlisted distribution.

You can submit your app via AppMachine like this:

  1. Click the Publish button in the top right corner of the Publish dashboard.
  2. Before your app gets published, AppMachine validates if all required information is entered and will notify your if some information is missing. Read more...
  3. You need to enter the What's new information, which is required by Apple for each release, except for your first release.
  4. Disable the switch Automatically release this version and click Next.
  5. Choose Manually release this version 
  6. Click Publish now

If your app is live or in review, you can submit this form with Apple to request unlisted app distribution.

If your request is approved, your app's distribution method will change to 'Unlisted App' and will automatically apply to any future versions of the app. A link will be generated with which users can download your app. If your app is already available on the App Store, then the current download link will remain the same.

Apps distributed through Apple Business Manager are not eligible for unlisted distribution. Changing the distribution method of Apple Business Manager apps over to unlisted distribution involves re-submitting the app to the Public App Store as a completely new app, before being able to put in the request for unlisted distribution with Apple.