For a Google Maps replacement, everything is going to work off of the base OSM maps, but OSMand is not a great app imo. Organic Maps is good if you want to be COMPLETELY FOSS, but if you want something with good navigation and real time traffic, Magic Earth is what you want. The app itself isn't FOSS afaik, but it's privacy oriented, has very few (if any?) trackers, and can be used completely offline.