According to the latest leaks, Xiaomi's upcoming Android TV dongle, the Mi TV Stick, will only support 4K on its upgraded variant.
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Xiaomi Mi TV Stick 4K Ultra HD Streaming Device, Android TV 11 with Google Assistant Voice Remote Control Streaming Media Player, Chromecast Built-in, 2GB 8GB HDR/AV1/2.4G/5G WiFi/BT 5.2, 2022 Latest