tvOS 13.4 (build 17L5251a) is an official Apple over-the-air update for the Apple TV 4 (2015), released on 2020-03-03T18:19:42Z. The update package is 422.01 MB. This is a delta (partial) update that requires 13.3.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 402766a4f0f1f2d192e57b820b51c05c2f8333f0.zip.