I helped bootstrap Mozilla's Location Service (MLS) to support geolocation on Firefox OS without Google Location Services. Mozilla even had its own Wi-Fi "wardriving/stumbling" app (MozStumbler https://github.com/mozilla/MozStumbler) and an opt-in stumbler in Firefox Android. But after Firefox OS was retired, Mozilla didn't have have a need for MLS. That said, Mozilla still runs a Wi-Fi geolocation service open to other projects (like GNOME's Geoclue service).
Mozilla also publishes cell tower location data and shares with the OpenCellID project. I worked with Mozilla's privacy and security teams to see if we could publish the Wi-Fi location data, but we didn't find a practical, privacy-preserving way to do that.
For more information about MLS (including a zoomable world map of the Wi-Fi location coverage), check out https://location.services.mozilla.com/