No iOS version as the other comment mentioned, but if you want to contribute, try Every Door ( https://every-door.app/ ) for now.

It doesn't have points and badges like Street Complete, but you can easily add/update/fix amenities, update addresses, add info about buildings, and fill in the same data using the "micromapping mode". I started with Street Complete, but now use this for most things.

I guess the OSM community is more defaulting to developing for other open platforms because that's what we mostly use ourselves and can test/run the code on, but iOS is in the making:

Pinned ticket "iOS - Planning": https://github.com/streetcomplete/StreetComplete/issues/5421

See also the project board: https://github.com/orgs/streetcomplete/projects/1/views/1 showing quite a few things already done, some in progress, and a handful todo or blocked each

The Go Map!! editor on iOS recently added StreetComplete-style quests.