So my internet service is horrible so I thought I could download 4k content onto a external harddrive then play those movies so thered be no chance of buffering. The thing is will my Android Tv box recognize a harddrive? I know it's work for a flash drive but I doubt a 4k 2 hour movie would ever fit on that.
If a flash drive works there's no reason I can think of that a hard drive in a USB enclosure wouldn't. At that point the Android TV should just recognize it the same way as a flash drive.
If you're looking to use this for mobile storage I would suggest a solid state drive in a USB enclosure. It takes less power to run and it's harder to break because there aren't any moving parts