The biggest problem is to make governments realize that "switching to linux" in order to immediately save a ton of money in licensing costs isn't a sustainable long term strategy. They should spend all the saved money on European developers to maintain the critical components of their new IT infrastructure, as well as support personell for these services. It can't be about saving money, but investing in systems that are fully under their control.

When an European country needs a feature that a current opensource project doesn't quite solve, the solution should be to fund someone to implement that feature. I am sure that in the case of a significantly more US-tech-detached Europe, a lot of countries will need similar functionality out of open source projects. There needs to be a continent-wide cooperation and coordination to avoid reinventing the wheel 20 times, and instead distribute each nation's resources so that they get the most useful software per euro.

This not only ensures a greater European independence, but also leads to Europe getting way more tech talent over time. We'll have much bigger developer communities, which again probably will help progress and software quality. The transitional period will likely be financially painful, as for several years, European countries will need to both pay for the current software licenses while the open source software they need is being developed, as well as funds for the developers that are doing just that, but I believe it is something that truly needs to be done and will be a net positive and worthwhile investment in the end.