If you can't spend 3 months in SF, you probably can't spend 3 months in any other european city/country.

Is there a city with anywhere near the critical mass of SF?

If that happened to be on the other side of the EU, would you be OK living a 3-hour flight away from Amsterdam, rather than a 13 hour flight away?

Is commuting back and forth 3-hours compatible with the "SF-level work ethic", as you call it?

Amsterdam to London is little more than 1 hour by plane.

And nobody checks your social media handles when you land.