Have you thought about adding an account management URL?

You could go to a page that listed many iOS wallets and instructions on how to add them.

Have you explored this at all?

There was a significant change in Apple's App Store policies that occurred in response to regulatory pressure and lawsuits, most notably from Epic Games. As part of this change, Apple announced that "reader" apps would be able to provide a single link to a website for account management, including payment setup.

"Reader" apps are a category of apps defined by Apple that provide previously purchased content or subscriptions for digital magazines, newspapers, books, audio, music, and video. Examples include Netflix, Spotify, and Kindle. Before this change, Apple's policy was to disallow any links or instructions that explained to users how to pay for their subscriptions outside the app, which allowed Apple to enforce its 15-30% commission on in-app purchases.