In the European energy market, the community energy sector is earmarked to make a significant contribution to the transition from fossil fuels to sustainable sources. Based on the diffusion of innovation model, large-scale development of community energy requires that the concept and the success of existing energy communities be widely communicated to potential participants and that user confidence be developed over time. In this paper, we present the architecture, design, prototyping, and testing of a digital support platform, co-designed with EU-wide energy communities, to support this process. The platform has been designed to engage early-stage or ongoing groups to progress projects and to connect and share experiences with other communities. This “community of communities” creates the necessary communication channel defined in the Diffusion of Innovation model. A transactional architecture for such a platform is outlined with clear links to all community energy actors. Based on this architecture, a prototype one-stop-shop (OSS) implementation is presented. Feedback gathered and lessons learned from beta testing with a representative group of end-users are outlined. The OSS architecture shows potential as a communications channel to expand the community energy concept and as a monitoring tool to track the progress of the energy community sector.