OpenMapChest Mapset
The easiest way to get a direct download of the mapset is make a small donation annually which helps to keep the mapset available. Click the Donate tab on the linked page and you will have instant access to the map files. You can still download the mapset for free, however you can't get it instantly, I think it is sent to you via an email link or similar.
A small $10-$20 donation helps to keep the mapset available. The last one I used from a Dutch creator was excellent and while using the same OSM data, the map distinguished different roads, minor roads and tracks much more clearly than the OpenmapChest one I am now using. It hasn't been updated since 2020.
Follow the instructions on this page via the Instructions Tab for installation to Garmin Basecamp for your specific platform.
When map is installed in Garmin Basecamp it is important to go to the bottom of the Map and ensure the "detail" slider is turned all the way up.
OpenMapChest Map
This is the Old OSM mapset that is no longer updated. As you can see it is much easier to distinguish track types on this map.
I have included a link to this file, I have both maps installed on my basecamp and reference both. The OpenMapChest map has current data though and is still being kept current, The old one from a Dutch creator?? is no longer updated and doesn't have as thorough track data as the OpenMapChest mapset. Consequently I go back and forth referencing between the two on my Basecamp.
The file on the button below is the Mac IOS version, its the only one I have.