And if you don't want to host Photon on your own you can have it hosted from GraphHopper: https://docs.graphhopper.com/openapi/geocoding

This request/response format is a bit different than the native Photon format, but with GraphHopper Geocoding it is possible to easily switch between different "providers" (like Nominatim, OpenCage etc.), which are all usable under the same contract.

disclaimer: I'm a co-founder of GraphHopper