Microsoft has released the latest version of Skype for Business (SfB 2019).

You can get it from MSDN or Volume License.

It gives support for Windows Server 2019, as well as cloud voice mail support or Cloud Data Connector.

You can check all the new here https://docs.microsoft.com/en-us/SkypeForBusiness/skype-for-business-server-2019 and removed features here https://docs.microsoft.com/en-us/SkypeForBusiness/deprecated