I use Maps.me as my main map and navigation app as I don't like that Google knows where I go, and I can say that it's a very good alternative to Google Maps. However I have to say that now I'm a little worried because it's Russian-owned. Happy to know that there's an open-source alternative.

There is an open source fork of maps.me maintained by original authors, who are not russian: https://organicmaps.app/

OsmAnd

Important clarification: OsmAnd~, installed from F-Droid. Do not install OsmAnd straight from the default app store.

Or do, if you want to monetarily support the developers in a convenient way.

If by “support” you mean “get nagged about the ‘pro’ version incessantly”.

By support they meant buying Pro version.

I did not have any nagging im the version I bought.