Short answer is yes you should be able to. But I just tried my linux formatted external HDD and the android system said it was not compatible and wanted to format... Which is a pain as kodi will read most drives. And works fine on my MiBox S android TV.
will have to check on FIL's workflow if that is acceptable. not quite sure how he puts his media files on to the hdd. my guess is via a windows pc, which might mean this is too much trouble for him.
haven't managed to convince him to use a NAS... he thinks it's a waste of power leaving devices on all the time... until fairly recently, he used to switch his router off at night.
thanks for trying it out, and the quick reply!