Cozystack is an open-source cloud platform built on Kubernetes. It turns bare-metal servers into a self-service environment that provides Kubernetes clusters, databases, virtual machines, load balancers and other services through an API. The whole platform runs on the operator's own hardware, and the project describes itself as a CNCF Sandbox project, under the Cloud Native Computing Foundation. Its source code is published under the Apache 2.0 licence.
The website names LF Projects, LLC as the legal entity for the project. That is a series of the Linux Foundation, a non-profit based in the United States, so the governance and legal home of the code sit in the US. The platform does not depend on a vendor-hosted cloud, because the data stays on the infrastructure the organisation runs itself. For a European organisation the main sovereignty question is therefore the quality of its own operation and the foundation's governance, rather than a foreign cloud provider's access to data.