OpenStreetMap, and the various clients for it. I personally am a big fan of Organic Maps, fast, responsive and clean. If you happen to be on iOS, I hear Apple Maps is also not as bad as Google, though also not open source.
For my use case of mixed public transportation i don't think there's anything OSM-based that comes even close to GMaps yet (i'd LOVE to be proven wrong here, i'm in the western EU area so lemme know if there's something i can try)
Is there an OSM client that has live traffic info or incorporates live public transport schedules? This has been the only thing keeping me from switching.
Waze covering up important areas of the map (such as junctions I was supposed to get off at) with adverts for local businesses was what made me rapidly give up on it.
Google going full on with the enshitification here