https://wccftech.com/apple-releases-beta-4-of-ios-12-3-macos-10-14-5-watchos-5-2-1-and-tvos-12-3-to-developers/

Today, Apple has seen fit to release the fourth developer beta of iOS 12.3, macOS 10.14.5, watchOS 5.2.1 and tvOS 12.3. The new beta builds arrive one week after the third developer beta. if you’re a developer, you can download and install the latest beta build right now from the Apple Developer Center. Let’s dive in to see more details on beta 4 of iOS 12.3, macOS 10.14.5, watchOS 5.2.1 and tvOS 12.3 and what do they have in store for users.

If you’re a registered developer, you can download iOS 12.3 from the Apple Developer Center or via over-the-air. Be sure to note that a proper configuration profile is required from the Developer Center. beta 4 of iOS 12.3 includes a new version of Apple’s TV app with a fresh look and enhanced functionality.