iOS 12.1 (build 16B92) is an official Apple over-the-air update for the iPhone 6s+, released on 2018-10-30T17:17:14Z. The update package is 1.34 GB. This is a delta (partial) update that requires 11.4 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: f8fe3e65a847f742699d12ee83ce90cc3dbd136a.zip.