There has been quite a few posts regarding Lemmy apps for iOS, and their installation process might not be straightforward since they're PWA or beta. Here's a list of apps mentioned and their links:
⭐ Released
Voyager (formerly wefwef) (📱PWA)
To install, open link in browser and follow instructions
It was submitted to the App Store with the last beta update. I predict it getting rejected because of the nsfw toggle. That created trouble for Apollo in the past.
your app includes user-generated content from a web-based service, it may display incidental mature “NSFW” content, provided that the content is hidden by default and only displayed when the user turns it on via your website.
Does lemmy support toggling NSFW content (or is it instance based)? I wonder if apps like memmy can leverage this toggle if it exists to pass the App Store review (don’t know much about how memmy currently does it).
Lemmy supports it on your profile, you should see a checkbox for "Show NSFW Content" if you click your username in the top right and then settings (if you're using the default web interface, anyway). I believe this is disabled by default. Instances can also block NSFW for the entire instance, there's an "Enable NSFW" option in the admin settings. This is also disabled by default.
Memmy itself has two settings, which look like they're independent of your Lemmy profile: one which enables or disables NSFW entirely (which is disabled by default), and one which can blur NSFW if it's enabled.
I suspect they'll raise an eyebrow or two with the App Store reviewers, but they do have prior art they can point to as well as that section of the policy you just posted. We'll have to wait and see; I haven't checked myself to see if they passed review or not.
First submissions typically don't pass anyway from what I understand for a myriad of reasons, so don't be surprised if it does get rejected. They'll just update the app and try again.