In Europe, there is now wide agreement that we need to build our "sovereign" alternatives to dominant big tech products and services, and that they need to be based on open source. However, which policies would be the right ones to reach the objective? What should governments do: write code, fund code, fund companies, fund maintainers, hire maintainers, whatever? Should they mandate the adoption of European and/or open software by policy? Should they leave everything to the market? The openDesk case can provide some useful insight on what can work in practice. The goal of this discussion will be to touch upon the recent debates surrounding the establishment of a Eurostack while comparing this to the practical realities of the development of open source in the European public sector.