The Fifth-Generation (5G) of mobile networks is designed to accommodate different types of use cases, each of them with different and stringent requirements and Key Performance Indicators (KPIs). To support the optimization of the network performance and validation of the KPIs, there exists the necessity of a flexible and efficient monitoring system, capable of realizing multi-site and multi-stakeholder scenarios. Nevertheless, for the evolution from 5G to 6G, the network is envisioned as a user-driven, distributed Cloud computing system where the resource pool is foreseen to integrate the participating users. In this scope, current monitoring solutions are limited, as they have to be able to maintain 5G performance in a distributed system with heterogeneous resources and still be efficient and sustainable. In this paper, we present a distributed monitoring architecture for Beyond 5G multi-site platforms, where different stakeholders share the resource pool in a distributed environment. Taking advantage of the usage of publish-subscribe mechanisms adapted to the Edge, the developed lightweight monitoring solution can manage large amounts of real-time traffic generated by the applications located in the resource pool. We assess the performance of the implemented paradigm, to confirm that it suits the requirements of the proposed scenarios, and discuss how the architecture could be mapped to other 5G or Beyond 5G scenarios.