I like to app. I used ArcGIS Pro 2.4, created a TPK using the Esri base imagery. I took the TPK with a few other layers and created a mmpk file. The mmpk file I created was saved to a local drive. I also uploaded it to AGOL.
I found that when I downloaded the AGOL version it saved it to Phone\Android\data\com.esri.explorer\files\mmpks.
I also found that I could put the local copy here Phone\ArcGIS\mmpks.
So it seems that Explorer will look in both these places for mmpk files.
Is it possible for Explorer to look on the SD card for manually added mmpks or to have the downloads go to the SD card?
PS. Another feature I also like is the ability to zoom in beyond the zoom level the TPK file was captured at. When I tried using a tpk of my own imagery, however, Pro did't recognize the tpkx file it just created as a valid file type when I tried adding it back to the map. I'll try again. Also, Pro refused to complete the mmpk creation when I used a definition query on a polygon layer to set the extents. This last issue may be a challenge if I want to create a map series of mmpks.
Lastly, the Explore for ArcGIS community place in Geonet says it doesn't exist or I'm not allowed in.