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
Using memmy at the moment. It’s the most advanced app right now. Wefwef is impressive as it resembles Apollo in an web app but at the end I prefer having a native app for daily use.
I have both but Memmy keeps logging me out and giving me all kinds of upvote errors. Wefwef works better and I think have pretty much the same functionality