tvOS 13.3.1 (build 17K5795a) is an official Apple over-the-air update for the Apple TV 4 (2015), released on 2020-01-22T18:08:30Z. The update package is 96.04 MB. This is a delta (partial) update that requires 13.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 4a68b48fa0dc806b5efa04b1974026cd20a3bce7.zip.