Have a look at Duplicati, it's free and open source (LGPL), Source Code on Github. It supports a lot of backup endpoints including of course local external hard drives.
It has a user interface, works on Windows 10 and supports encryption.
Check out this link.
Heaps of options, and it does mention open source options. All will use OpenStreetMaps as the map and routing.
The Maps.Me solution looks pretty good - https://wiki.openstreetmap.org/wiki/MAPS.ME
Navit seems to be more focused on in-car navigation, which might be more suitable depending upon ...