macOS Server 5.6.3, released on , stands as a pivotal "bridge" version in the history of Apple's server software. It was specifically designed to be the final version for users on macOS High Sierra (10.13.6) who needed to maintain traditional "open-source" server features before Apple's radical shift toward management-only tools. Core Purpose and Compatibility
This version is the ultimate release for macOS High Sierra 10.13.6 . macOS Server 5.6.3
It served as a preparation point for the subsequent macOS Mojave-compatible version (5.7.1), which removed the vast majority of server features. The "Deprecated Services" Turning Point macOS Server 5