If there’s not on the F-Droid, on the google store is cool too.
The official OSM wiki has a nice chart with android apps: https://wiki.openstreetmap.org/wiki/Android#Navigation (There are also non navigation apps somewhere else on that site)
As someone else already said Magic Earth is great as a direct google maps alternative, I use it in combination with organic maps which I find better when on foot or looking around on the map.