The Facebook Android[2] and iOS[3] SDKs are source-available.
From a privacy perspective, when someone compares Google Maps to HERE WeGo, the question is whether using Google or HERE (plus the Facebook SDK) would be more of a privacy violation. I don't have a good answer to this question.
But from a market share perspective, HERE WeGo is a minor player compared to Google and using it instead of Google Maps would help curb Google's market dominance in mapping.
Of course, if a free and open source OSM-based app is viable for your area, I would go for that instead.
[1] https://f-droid.org/it/packages/com.celzero.bravedns/
Well unless you absolutely never use Google (which is hard), you're better off using Maps (as they track you anyway from occasional usage), where as it's easier to never use Facebook (in fact all Facebook IPs are outright blocked on my networks) so it's better to not provide any data to them at all.
So for me if I had to choose I'd prefer Google (who probably track me anyways during occasional usage of their services) over Facebook which aren't supposed to track me at all since I never use their services (and since I avoid all apps with FB malware in them, I don't think they can track me).
In my case I use Apple Maps which works well enough for me. I wish OSM-based alternatives were as good when it comes to POI searching but in London I found that OSM is even worse than Apple.
* https://joemorrison.medium.com/openstreetmap-is-having-a-mom...
It may have changed since then and if so that's great!