OSMand is a very advanced and highly usable free software map and navigation program for Android. It supports downloading map packages of geographical areas or countries for completely offline navigation, using it does not require any online connectivity.
Features And Usability
OSMand allows you to download map files generated using OpenStreetMap data. There are files for small geographical areas and whole countries. The files covering countries can be quire large, you may need 3-5 GB to get map coverage of the country you are in. It is also possible to download Wikipedia data files to get rich data about locations overlaid on the map. The price of some flash or SD card storage gets you entirely offline navigation; no Internet connection is required to use OSMand to view and use maps. You can search, plan and follow routes and lookup map markers and use all the features OSMand has to offers without any Internet (3G/4G/5G) connection.
OSMand supports route navigation. It works great.
Verdict and Conclusion
OSMand is the best free software map program in existence. It is only for Android, GNU/Linux desktop users will have to use the much more limited desktop program GNOME Maps (currently the best map program for desktops).
A full free version of OSMand is available in the free software F-Droid appstore/catalog. A slightly more limited version is also available in the Google Play Store.