As a legacy version, 5.6.3 has developed several significant maintenance challenges for those still running it:
for new installs; fully functional for existing upgrades. Management Tools (Profile Manager, Open Directory, Xsan) Active and supported as the primary focus.
(Caching Server, File Sharing, Time Machine Server) macOS Server 5.6.3
Does 5.6.3 delete deprecated services? - Apple Support Community
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 As a legacy version, 5
Compatible with Macs capable of running High Sierra, including Late 2009 MacBooks and iMacs, and Mid 2010 Mac minis, Pros, and MacBook Pros.
(Mail, DNS, DHCP, VPN, Websites, Wiki, Calendar, Contacts) - Apple Support Community It served as a
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