Another quick hit little bug for you.
Despite enabling Gallery access on the MDX App settings, for some reason on Android access to the upload from device page was being blocked when “document Exchange (open in)” was set to restricted.
If you lifted this restriction, all worked well. but Nobody wants that.
Anywho, with much pain and wandering around the Google Android Developer documentation, the following exception list allows you to restrict the App successfully while still allowing access to local files for upload.