In this talk, I would like to present the importance of the core Collaborative Softwares using by individuals and companies in this stack and the progress and challenges of the Open Source communities providing alternative solutions and the importance of all European countries to collectively support the actors in the Open Source communities providing solution in this area. In the latest years, the subject of European Digital Sovereignty is gaining ground. Clearly the dominant position of the BigTechs is making both European companies, Countries but also individual increasingly dependent on the product and services of the BigTechs. In order to regain our sovereignty we need to look at the full stack, from hardware, to cloud and to the software running on those hardware and clouds. In this talk, I would like to present the importance of the core Collaborative Softwares using by individuals and companies in this stack and the progress and challenges of the Open Source communities providing alternative solutions and the importance of all European countries to collectively support the actors in the Open Source communities providing solution in this area. I will show the progress made in the last years by different providers of Open Source solutions (NextCloud, Matrix, BigBlueButton, Jitsi, XWiki, CryptPad and many others), describe the challenges and difficulties when building Open Source products and competing with the extremely powerful actors that we are facing (including monopoly abuses), but also make proposals on how we could make them work better together.