tvOS 12.1.2 (build 16K5534a) is an official Apple over-the-air update for the Apple TV 4 (2015), released on 2019-01-07T18:15:35Z. The update package is 1.37 GB. This is a full OTA update that can be applied from any compatible base version. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: d43467292414038897184d6bce019531375c5c55.zip.