Mitigating cybersecurity threats in power distribution grids requires a testbed for cybersecurity, e.g., to evaluate the (physical) impact of cyberattacks, generate datasets, test and validate security approaches, as well as train technical personnel. In this paper, we present a blueprint for such a testbed that relies on network emulation and power flow computation to couple real network applications with a simulated power grid. We discuss the benefits of our approach alongside preliminary results and various use cases for cybersecurity research and training for power distribution grids.