Apple releases watchOS 5.3 beta 1 to developersInstalling the watchOS 5.2.1 beta is more complex than an iOS or macOS beta, but it's also for developers only.
Of Apple's four primary operating systems (iOS, macOS, tvOS, and watchOS), only watchOS lacks a public beta, which isn't surprising, given how comparatively complicated is. You need to install a certificate on your Apple Watch, then download the software to your iPhone running the iOS 12.3 beta, transfer it across, and get it up and running. It's not hard, but it does take patience and you may have to troubleshoot.
What's new in the watchOS 5.2.1 beta?
May 15, 2019: Apple releases watchOS 5.3 beta 1 for developers
Apple has just released watchOS 5.3 beta 1 version for developers. If you already have a previous watchOS 5 beta installed, proceed to the Watch app on your iPhone running the beta of iOS 12.4 and download away. If you were waiting to begin watchOS testing with version 5.2.1, now's the time to download and get started.
May 7, 2019: Apple releases watchOS 5....
Source:
Apple releases watchOS 5.3 beta 1 to developers
