OpenATv has problems with Xcplugin :)
The procedure is simple:
If box is installed exteplayer: you can select it on XCplugin.
Otherwise you can not select it
Of course if the plugin is configured EXTEPLAYER3 even on the puzzle must be EXTEPLAYER3 otherwise it will not work.
Maybe you do not find it in SERVICEAPP plugins but in settings - I believe
Exteplayer better than gstreamer? Yes
cheers