When Marble Maps is installed on your smartphone and you open any kind of file in a file viewer, Marble Maps will be offered as a choice to open the file with. In this task this should be fixed: The mime type registration needs to be more specific such that Marble Maps is a choice only for .kml, .osm and .gpx files.
The mime type registration can be found in src/apps/marble-maps/package/AndroidManifest.xml. Make sure to test your fixed mime type registration on the device with various .kml, .osm and .gpx files you downloaded on your smartphone.
The result of this task should be a review request in https://phabricator.kde.org/ (Differential) containing the working and tested implementation.