The Utility Network solution pages refer to a specific version of the Utility Network Management extension, e.g.
Electricity asset package v3.1 --> ArcGIS 2.4 with version 3.0 of the ArcGIS Enterprise Utility Network Management extension
Gas asset package v2.0.1 --> ArcGIS 2.3 with version 2.0 of the ArcGIS Enterprise Utility Network Management extension
The versioning of UN management extension is not clear ot be. I am correct to think that
version 2 --> Portal, ArcGIS for Server 10.6.x
version 3 --> Portal, ArcGIS for Server 10.7.x. Is this then not supported on 10.6.x?
Other than licencing the UNM on the server, there isn't anything else to install on the server that has a version.