Android TV. Firmware: 5.0 Lollipop (API 21) and later.
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Amazon Fire TV Devices:
Fire TV Cube (2nd Generation), Fire TV Cube, Amazon Fire TV (3rd-2nd-1st Generation), Fire TV Stick 4K, Fire TV Stick (2nd Generation), Fire TV Stick Lite, Fire TV Stick (3rd-1st Generation) and Fire TV Edition Televisions (Grundig, Insignia, JVC, Nebula, Onida, Toshiba and OK). More info