tvOS 12.3 (build 16M153) is an official Apple over-the-air update for the Apple TV 4 (2015), released on 2019-05-13T17:20:37Z. The update package is 323.34 MB. This is a delta (partial) update that requires 12.1.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 22b93bc4f08e837ef239ccac62c0dc3b67f833f3.zip.