Btw, NRC has a nice podcast series on the topic. One thing hampering the sovereignty effort is the enormous amounts of Azure/AWS/GCP certified people. Their career is build on these platforms.
Currently I'm involved in projects surrounding https://developer.overheid.nl/kennisbank/security/standaarde... . Have a look there. It's not FLOSS in the way that you can just provide PRs of things you'd like different, but FLOSS in the way that you can get in touch and with enough expertise, have people listen to you.