photon VS Acastus

Photon by Komoot is also using Elasticsearch for validating addresses and locations.

Alternatively, you could run your own Photon API: https://github.com/komoot/photon

Open Source. The routing server is open source too and geocoding too.

To fully self-host a route planner (e.g. a "Google Maps" equivalent) you need GraphHopper for the routing and two other parts: you also need some visualization aka "maps" (e.g. with OpenMapTiles) and you need the address search (e.g. with Photon).

There exists photon, but I don't know if it's used in any libre mapping app.

Acastus-Photon is an Android app that allows you to search up any address or point of interest on OpenStreetMaps and open it in OsmAnd or any other maps app. It relies on photon as it's open-source backend server (provides elasticsearch for OSM), so you can either use a public instance or self-host. This allows you to have search functionality as powerful as Google Maps whilst being able to use solely open-source software instead.

I use https://github.com/gjedeer/Acastus From Fdroid

actually, now that you ask about it and I try it, sharing directly to osmand isn't the best solution, as osmand handles shared addresses kinda weird. after a little research and experimentation, I found using an intermediary app called Acastus, which you share the address to, and it converts the address to GPS coordinates for osmand. it asks for location permission for using the address of your current location but works fine for this case if you deny it.

Acastus-Photon (version 1.26): An online address/POI search for navigation apps

Acastus Photon translates a postal adress to a geographic cordinate that can be shared.