Most desperately missing on #Mobian: An offline #OSM #maps app. E.g. #mepo, #organicMaps, or #pureMaps. EDIT: and #osmin!
When I had an Android phone some years ago, I used #OSMAnd, which was good enough for me.
OrganicMaps is in the #Debian new queue since June, btw. But the Linux UI is not as usable as the Android one.