onigino
which apps use geocoding feature?
One example I know of is the NeoStumbler app, which uses reverse-geocoding to show addresses instead of only showing GPS coordinates.
As @GrapheneOS wrote in the release notes, only a tiny subset of apps need this.
how do I use this feature
You need to go to Settings -> Location -> Location services -> Geocoder, and ideally set it to GrapheneOS proxy.
would be a great for osmand and others that don't do address search very well
OSMAnd uses Nominatim, the same geocoder used by GrapheneOS, so this won't make a difference at all. I also don't believe that they're using the Android Geocoding API for the internal search feature.