The last time I looked for an alternative for Google/Apple Maps some months ago, I couldn't really find a decent OSM (or even Mapbox)-based app for iOS. Any recommendations from anyone?
I really like the web-based Openroute Service [1] that was shared here recently, but AFAIK this doesn't have an app version.
Personally, I use Maps.me for simple tasks like finding street, shop or other POIs. OSMand is my favorite tool when navigating during cycling trips because of far more advanced rendering options. Both apps are great.
Osmand, as the name implies, is Android only, though. Not a problem for me, since I use the fdroid version, but OP was specifically asking for an iOS app.
EDIT: as below, I stand corrected. Please ignore my false statement above.
I think the issue is that for the mass market, OSM is a technical detail that the apps only mention in passing, if at all.
The best iOS apps with OSM I have found are [Guru maps] (formerly Galileo) and [Pocket Earth]: Have been using paid versions of both for the last 5 (?) years, switching back and forth. Currently on Guru after they added contour maps and offline routing a while back. Haven't checked if Pocket has this yet...
I found OSMand to be terribly slow on my old phone and maps.me sort of OK-ish in performance. My phone is quite old. Searching locations in both of them is not perfect. One sometimes needs to know how to search for things and treat the UI carefully, patiently waiting till it has finished showing results.
Searching locations (geocoding) is never perfect. Google seems to be the best at it, though. Probably because they've put significant effort into doing that specifically and they simply have access to more data than any other organisation. OSM isn't about geocoding, it's about building a geographic database of the world. Geocoding is just one application and not one that seen a great deal of attention, relatively speaking. Personally I often use Google maps for geocoding if I have to but most of the time I already know where I'm going on the map so have no need for it.
Unfortunately, Maps.me on android is either replete with trackers or now basically doesn't work (the f-droid expurgated version), though the question wasn't about android. At least that was the case with f-droid fairly recently -- due to changes in how the maps are now distributed as far as I remember.
I really like the web-based Openroute Service [1] that was shared here recently, but AFAIK this doesn't have an app version.
[1]: https://maps.openrouteservice.org/directions