maps

The Mini has no maps at all. What device do you have?

The inreach explore plus

Moved to the correct forum.

The Explorer+ is a legacy device. It still uses maps in the old DeLorme format. The only maps that are available for the device are those which you can install from the Map tab on your account at explore.garmin.com.

Beginning with the newer GPSMAP 66i and the Montana 7x0i, the new inReach devices are full members of the Garmin ecosystem. They can use any maps compatible with Garmin handhelds in general. That includes both maps purchased from Garmin and third-party compatible maps such as OSM or the maps available from gpsfiledepot.

I very much doubt that the legacy devices will ever be made compatible with Garmin maps.

To add to twolpert's answer: 

1. The OSM maps Garmin uses on the Explorer+ are updated about every 6 months, according to what they told me several years ago.  That may be different now.

2. Be aware that some of the map layers you add to your device (from the Map tab) are not transparent.  For example, if you enable Topo North America, it will hide trails/roads from the BLM layer.  This is location-dependent of course (my use is in the U.S. Western states).  So if in doubt I check by alternately enabling/disabling those particular layers.  (The others seem to be transparent.)

I mount my iPhone on my KTM 450 and use the Earthmate app with my inreach on. However I get extremely frustrated trying to figure out waypoints, routes, tracks, and everything else necessary prior to riding.