tvOS 11.3 (build 15L5208a) is an official Apple over-the-air update for the Apple TV 4 (2015), released on 2018-03-13T17:05:56Z. The update package is 55.67 MB. This is a delta (partial) update that requires 11.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 66b8d3fc100c42bacf7b9f70631131e79a6ab2a3.zip.