Organic Maps is the most private offline map app, it looks prettier than Google Maps and Apple Maps, it leverages data from openstreetmap that you can update easily compared to the competitors, it’s very battery efficient and the best of all its FOSS.
My main issue with organic maps is the lack of public transit routing. There seems to be a way to use GTFS - but you have to manually download the data and build the app…
Long term there might be a way - but unfortunately not ready yet
Edit: I found OsmAnd that has public transit routing 🙌