Fire TV Cube has a Micro USB port for an Ethernet Adapter and an Infrared port

Fire TV Cube

USB to Fire stick adapter connects a video streaming device such as the Fire TV (3rd generation), Fire Stick 4K (2nd generation), Fire TV Cube, Google

Cable Matters Micro USB to Ethernet Adapter Up to 480Mbps for Streaming Sticks Including Chromecast, Google Home Mini and More - Not Compatible with

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Inteset USB 2.0 & Micro USB OTG Y Cable for Controlling The F-TV Stick, Pendent, or Cube, Supports Wireless Keyboards and The IReTV for Universal Remote Control. (IReTV not Included)

Fire TV Cube Review: A Blazing Fast Streaming Device

Everything you can do with the Fire TV Cube's Micro USB port — Ethernet, App Storage, External Drives, Peripherals, FLIRC, OTG, and more