There are a few Apollo-likes for iOS. One I contribute to is Mlem:

https://github.com/mlemgroup/mlem

I've been using Memmy[1,2], which is similar to Apollo.

1: https://github.com/Memmy-App/memmy

2: https://apps.apple.com/us/app/memmy-for-lemmy/id6450204299

That's Voyager, you can test right away as PWA on m.lemmy.world or native app.