watchOS 5.3.8 (build 16U680) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm, LTE), released on 2020-07-15T17:28:40Z. The update package is 54.65 MB. This is a delta (partial) update that requires 5.3.5 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 4a40aaf240efb55cdb7d3a98f4ef5d67bf3ec240.zip.