iOS 12.1 (build 16B92) is an official Apple over-the-air update for the iPhone 6s+, released on 2018-10-30T17:17:06Z. The update package is 1.85 GB. This is a delta (partial) update that requires 10.3.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 765282bca78bd95a0a8474b1797ed576560ec742.zip.