> You start with the very end of the chain

No, that's just taking a quick win and kicking the can down the road.

Data migration and hosting is comparatively quick and easy. It can be done any time.

What takes huge lead-times is re-establishing a chip-making industry; not just the fabs but also the raw material contracts, materials processing etc

I'd argue that achieving data sovereignity first is counter-productive because we know the politicians will relax once the easy bit is done. The actual hardware hard-work will never get funded, especially after a new US President takes office in 2029. Europe will sigh in relief and go back to its wilfull ignorance of the risks of dependency'