The document describes the work that has been done to work towards interoperability between DestinE and interTwin through their respective Digital Twin engine (DTE) software components, through the implementation of specific use-case and pilot studies. It includes results and lessons learned with respect to interoperability between the two DTE implementations and an outlook towards future developments and improvements. The document can serve as a guideline for other communities that could be onboarded in DestinE, complementing other initiatives towards evolving and expanding the Digital Twin ecosystem in DestinE.