watchOS 6.0 (build 17R5575a) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm, LTE), released on 2019-08-27T17:30:15Z. The update package is 740.9 MB. This is a delta (partial) update that requires 5.2.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 61db8a163c43f37ade3b7d8bf4048d35bb81c426.zip.