The writing has been on the wall for macOS Server app for a long time. With the introduction of High Sierra, many of the Server features have found their way into the client version but in spring 2018 macOS Server is having a major overall to focus more on management of computers and devices.
A number of services will be deprecated and/or will be hidden on the update to of macOS Server coming in spring 2018. If service been previously configured, you’ll still be able to use with that updated version.
Apple said that the deprecated services will be removed in a future release of macOS Server, so if you are using these services, you should consider alternatives. In knowledge article HT208312 (https://support.apple.com/en-us/HT208312) Apple supplies a list of links to potential replacements for each service.
Here’s a list of services that will be deprecated: