How can I distribute an iOS app to 50k users by invitation only?

Question

I have a client who wants to deliver the app to 50k specific users, at start. Then he wants to go public with the app after some time. However, this could not be seen by users as beta testing, since it's just an "exclusive" earlier possibility to access the app, not tests.

We know these users since they are a part of other service users group. We will probably create accounts for them and distribute login/one-time-passwords by invitation or give them the possibility to log in with credentials from the other service.

I've been searching for the solution (e.g. https://www.knowband.com/blog/mobile-app/share-ios-app-without-publishing-on-apple-app-store/) but still, I'm not sure which way to go. We're still in the middle of development so we can provide a possible solution and even make changes in the onboarding/login process. But we have to have a decision on this matter.

From possible solutions:

1. AppStore - we would not give the possibility to register in the app and just people with credentials could log in. But is it even possible with an iOS app and not be rejected by Apple? I know that many apps don't have registration within the app (e.g. banking apps) - how do they do that? They just say that registration is available only on some www/in person at the bank and you receive credentials to your account somewhere else?

2. Enterprise distribution - this is probably not possible since users won't be employees of my client. These are regular people.

3. VPP - I've heard about it recently and never tried it but isn't it just a "simpler" Enterprise solution and shouldn't users be also employees of my client? Can VPP apps be changed to regular AppStore apps afterwards?

I think right now option 1 seem the most possible one since the app will be distributed to all the users after some time (we will add registration then). Any ideas on the matter? How can we not be rejected using solution 1 during a review?

Answer 1

Solution 1 is possible, you provide apple with certs in App Store connect when you submit to the store. Specifically the field 'Sign-in required'

I would do that, it's got very little time overhead as compared to the other two.