I'm currently learning how to load data into ArcGIS Utility Network using Esri data loading tools, Utility Network Foundations, and Utility Network Package Tools as per this tutorial . So far I've successfully migrated the Utility Network layers like pipeline, pump, valve etc. What about standalone non-UN layers/feature classes from the source database? For example: dam, spot height, water bodies & district boundaries.
One method that I can think of is using Append to migrate these non-UN layers/feature classes.