There are 'work arounds' that involve being enrolled in the Enterprise Developer Program, but you're still at Apple's mercy. If they believe you're not sticking 'to the spirit of the program' (e.g. using it just to get around the App Store) they'll terminate.
Do you have a source for that that you can link me to? Because from this, I get the impression that is not the case: https://support.stripe.com/questions/apple-and-stripe-tos-an...
Basically, your app is not allowed to have any links to sign up, or to your website, and you can do this for eg a SaaS app.
The idea is that then you're not using the app store for marketing, it's only for servicing your existing users.