mlem is currently being developed for iOS with around ~20 contributors. It's in early open beta, and I'm psyched because there's supposed to be a massive update between now and tomorrow.
memmy for iOS looks promising. Really intuitive 'swipe to upvote/downvote/reply' feature and browses similarly to Apollo. It's very barebones right now, the project is just a few days old and there's one developer (as far as I know).