iOS 12.3 (build 16F5148a) is an official Apple over-the-air update for the iPhone 6s+, released on 2019-04-29T17:36:13Z. The update package is 415.37 MB. This is a delta (partial) update that requires 12.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 16c42d059a255d183325bfc2192eb0b00b8dbee0.zip.