It's probably considered anti-competitive but let's image they scrap 1 billion of their budgets and invest in opensource:
- polish Samba to be a viable Windows Server replacement. Replication, missing Kerberos functionality, Implement ADWS, ADFS - maybe Exchange APIs. Save millions on server costs.
- unfuck LibreOffice, develop a strong foundation to implement typical processes
- polish KDE / Plasma to macOS/Windows usability/stability - rewrite kmail/korganizer with modern usability/ui
Not sure if that's possible but it feels like a lot of things are 60-80% done - maybe taking a leap and fixing the other 60-80% might make a difference.
- have an EU wide service agency that supports municipalities in implementing OSS
- demand opensource software for public money.
- create strong open standards and enforce them by law for public institutions.
maybe it will take 5 to 10 years but everyone should profit.