Addendum aims to provide communities with the tools to independently and sustainably manage their digital communication and data exchange infrastructure. The core software component, "Medienhaus/Spaces," is a FOSS platform based on the [Matrix] protocol. This protocol facilitates the creation of decentralized networks, allowing interaction with other communities, organizations, or institutions while maintaining control over their data and software.Addendum expands on this by offering a holistic hardware infrastructure solution. The project includes an autonomous server equipped with an innovative battery management system, integrated into a rotating solar panel. This design allows the digital infrastructure to be entirely self-sufficient. The solar panel charges the built-in lithium-polymer batteries (LiPos) during the day and ensures the web platform's accessibility via Wi-Fi or LTE.The primary focus of Addendum is to achieve comprehensive digital autonomy. It is not sufficient to run free software that ultimately depends on large providers' data centers like Amazon. Instead, Addendum envisions a fully autonomous and climate-neutral digital infrastructure. The name "Addendum" reflects this extension of thought, emphasizing the necessity of considering climate-neutral operations in FOSS projects.Addendum serves as a blueprint for an autonomous digital infrastructure, demonstrating that both software and hardware can be independently operated while still enabling interaction with other networks through federated protocols. This project is conceived as a response to the climate crisis, showcasing the feasibility of sustainable and self-sufficient digital infrastructure.All project plans and software are Free and Open Source, available for anyone to use, modify, and share. Addendum aspires to inspire other projects to develop climate-neutral and autonomous digital infrastructures, setting a precedent for future developments in this field.