Location apps are led by offline maps built on OpenStreetMap data. Organic Maps is a privacy-focused offline map with navigation for hiking and cycling, and OsmAnd is another full OpenStreetMap client. MAPS.ME was popular but is now marked as unmaintained. Both work without a network connection once you download a region, and both have App Store links.
Tracking apps are the other big group. OwnTracks keeps a private location diary or shares location with family, Traccar Client reports device location to a Traccar server, and Arc learns the places you visit. iBurn is an offline map for Burning Man, ParkenDD shows parking availability in Germany and Switzerland, and KartaView collects street-level imagery. These projects show Core Location, background location updates and MapKit or custom map rendering. Background location needs a clear reason in App Review, so read how each app explains it to users.