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.
Full support for publishing to a standalone ArcGIS Server site (not federated with a portal) became available with the ArcGIS Pro 2.4 release in June 2019. This support requires that the ArcGIS Server site is running ArcGIS Server 10.6 or higher and supports map services, feature servicew, image services, geoprocessing services, and geocoding services.
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.