The ability to publish to services to an ArcGIS Server site that is federated to a portal has been available since ArcGIS Pro 1.2 and ArcGIS Server 10.4.
As of ArcGIS Pro 2.3 the ability to publish to a standalone ArcGIS Server site (not federated with a portal) is partially implemented with support for publishing map services (including the Feature Access capability to enable feature services) to a standalone ArcGIS Server site (10.6 or higher) using arcpy scripting. Additional functionality is planned for ArcGIS Pro 2.4 to be released in June 2019.
See this comment for further details: https://community.esri.com/ideas/12258-arcgis-pro-publish-services-to-arcgis-server#comment-72791
I heard that ArcGIS Pro cannot publish map or feature services to ArcGIS Server. It would be great if it could just like ArcGIS Desktop.