iOS 13.4 (build 17E5249a) is an official Apple over-the-air update for the iPhone 6s, released on 2020-03-03T18:20:15Z. The update package is 711.1 MB. This is a delta (partial) update that requires 13.3.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: d2e9f21bd3c21f3ab0166a152ce8f78c71584b5f.zip.