Developer who is a member of Apple’s paid Developer Program are receiving the macOS High Sierra 10.13.5 beta update if they have the appropriate certificate installed on their Mac.
For public beta testers, the update should appear in a few days. The Apple Seed program is free and offers subscribers access to iOS, macOS and tvOS betas. The betas are not always stable and should not be installed on a primary device, especially not if it is the only Mac available to the user. In any case, a backup should be made in advance to return to its former state if necessary.
Users are waiting for some features planned for both macOS and iOS, including news on the iCloud, a feature that was included in the previous betas but later retired. Messages in the iCloud have been reintroduced in the iOS 11.4 beta and are also included in macOS High Sierra 10.13.5.
The previous update to MacOS High Sierra 10.13.4 includes support for external GPUs (eGPUs) as well as business chat in news and several other bugfixes and minor feature enhancements, as well as security updates.