We've had similar problems with keeping Zulip in the Apple app store. It's incredibly unpleasant to deal with this aspect of publishing an open source application.
For context, Zulip is a 100% open-source team chat project (in the same space as Slack/IRC/etc.). You can self-host Zulip, which we've put a lot of effort into making easy, or host it on Zulip Cloud (with both free and paid plans). There's no individual subscription option for the product at all -- just like with Slack -- so the app store policies to enforce their monopoly by requiring all individual purchases be taxed by Google/Apple shouldn't even apply to us.
But we've still had multiple rounds of rejections caused by aggressive enforcement of these policies:
* A couple years ago, Apple reviewers repeatedly rejected updates to the app because the privacy policy / terms of service pages linked from the app contained the zulip.com website footer, which in turn link to the pricing page for Zulip's paid offerings. This means our Privacy Policy could be a way to get people to buy something without paying the Apple tax! We "resolved" this, on the advice of their appeals expert, by passing a special parameter when loading these pages from the ToS/Privacy links in the mobile apps that hides the header/footer sections of the page :(.
* In May, Apple reviewers repeatedly rejected the Zulip mobile app for linking to its own source on GitHub. At first we thought the problem was that we had recently set up GitHub Sponsors [1]. Further correspondence determined that the problem was even more ridiculous: Any GitHub page has a tiny link in the https://github.com/zulip/zulip-mobile footer for GitHub's own pricing! We were able to convince them to approve it in the end, but we were close to giving up and removing the GitHub links. I'm still upset about the whole experience because it was a huge waste of energy.
It's not clear to me whether these rejections are what Apple's policies intended or just the policies being incorrectly applied. But it doesn't really matter: these appeal processes are opaque and scary and mostly consist of them repeating what you need to change with minimal explanation. If not for the entrenched monopoly, we'd be looking to switch to another vendor that wasn't so sloppy about something that's very important to us. I think the harm caused by sloppiness on the part of monopolies doesn't get enough attention.
[1] This would have been wrong too, though I do know some companies use a Patreon as the way to sell their product, and I can imagine that being a workaround that Apple would be on the lookout for. But it's easy to check that we're definitely not playing that game.