https://www.reddit.com/r/privacytoolsIO/comments/jpgbdm/firefox_uses_google_geo_api_by_default/
QuoteI've noticed that Firefox uses google api for geo location lookups (at least in Linux version).
you can verify that by going to about:config and search for geo.provider.network.url. it has a value similar to https://www.googleapis.com/geolocation/...
you can change the value to https://location.services.mozilla.com/v1/geolocate?key=test (as suggested here) to use Mozilla API.
you can also change its value to something like data:application/json,{"location": {"lat": 40.7590, "lng": -73.9845}, "accuracy": 27000.0} (as suggested here) to fake your location.
I'm on an older FF version on Debian so it must be a new change. Obviously "wtf" why they chose a Google API as a default when they have their own equivalent, but also a nice way for you to let sites know your chosen location.