

Organic Maps gets their map data from OpenStreetMap (OSM). All OSM stuff is open source and the data is entered in by volunteers. If your area doesn’t have much yet, you should consider being the change by adding your favorite spots!
Other people have mentioned things like StreetComplete, which is an app that helps you fill in the gaps of some OSM data.
I can’t seem to find any information on it, but how hard would if be to host your own Bridgy Fed? I feel a tool like this would ideally be decentralized.