iOS 15.7.4 (build 19H321) is an official Apple over-the-air update for the iPhone 6s+, released on 2023-03-27T17:12:54Z. The update package is 1.23 GB. This is a delta (partial) update that requires 15.2.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 45427aed6c045a2f85f282299ae9120fd5967be1.zip.