Key Enabling Technologies (KET) support the adoption of Industry 4.0 (I4.0) and are also considered the main drivers of the Circular Economy (CE) transition. In this respect, the guidelines and real use cases to inspire enterprises and industry to lead the twin digital and green transition are still poor. This work is aimed at contributing to this matter, with twofold goals: on the one hand, to show a depth desk-research analysis of the key existing policies at European level that foster this twin digital and green transition; on the other hand, to review practical use cases and international projects where CE practices are boosted through the implementation of KET. From the analysis, a set of recommendations are suggested as a guide for policymakers, researchers, and industry managers on how to foster the CE through the implementation of I4.0 technologies.