As of April 21, 2022, Apple has discontinued macOS Server. Existing macOS Server customers can continue to download and use the app with macOS Monterey.
The most popular server features—Caching Server, File Sharing Server, and Time Machine Server are bundled with every installation of macOS High Sierra and later, so that even more customers have access to these essential services at no extra cost.
As Rich Trouton has pointed out, there were two services still in macOS Sever without an equivalent in the client version: Profile Manager and Open Directory.
With the rise of some really solid third-party MDM solutions, the writing has been on the wall for Profile Manager for a while. In that support document, Apple links to two more articles. One is about choosing an MDM solution and the other is about planning an MDM migration.
Open Directory was Apple’s take on LDAP, and while I am sure some will be sad about it going away, I haven’t seen it in the wild in a long time.
Back in the day, I managed quite a few OS X Server installations, but the truth is that the market of third-party solutions that Mac shops can enjoy today simply overtook what Apple was doing.
The biggest problem? I don’t think Apple’s heart has been in server space for a long, long time. The Xserve has been dead for over decade, and OS X Server went from a full-blown operating system to an application since the days of Lion. In short, today’s news shouldn’t be surprising to anyone paying attention to this corner of the market.