tvOS 12.1.1 (build 16K5045a) is an official Apple over-the-air update for the Apple TV 4 (2015), released on 2018-11-29T18:09:22Z. The update package is 185.5 MB. This is a delta (partial) update that requires 12.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 26dc25572dd16d0a6674c95b2fa273d134132d23.zip.