Apple has announced through a support document that macOS Server, its operating system for server hardware, has been discontinued.
The end of macOS server comes just over 23 years after its introduction on March 16, 1999. The final version of macOS Server is 5.12.2.
During the latter part of macOS Server's run, Apple incorporated many of its features into macOS as part of a phasing out of the software.
For example, the File Server, Caching Server, and Time Machine Server were included in macOS High Sierra. The command-line tools to manage Xsan (Apple's storage garage network/clustered file system) were included in macOS Big Sur.
Apple had been removing many features starting with version 5.71, and its support document lists alternatives to the removed features if they are not in macOS.
The remaining feature that administrators will have to replace with the end of macOS Server is Profile Manager for mobile device management (MDM), and Apple has a document to help choose an MDM solution.