iPadOS 12.3 (build 16F5139e) is an official Apple over-the-air update for the iPad Pro 3 (11-inch, Cellular, 1TB Model), released on 2019-04-22T17:08:34Z. The update package is 382.06 MB. This is a delta (partial) update that requires 12.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: b980f8bd17b081e0e37b9bed847a7127c02c7e8d.zip.