Just German, not European, but still a start: https://en.wikipedia.org/wiki/Sovereign_Tech_Agency

The problem was more than remuneration. It was burnout and mental health issues. They may have been moderated by income but we don’t know.

Also today as I understand it much of OSS is done in-house by major companies (red hat, Ubuntu, ibm, Google, etc)

I don't think it's a money thing really. IIRC the regular XZ creator/maintainer had a regular job and enough money already, and it was more of a burnout thing from dealing with the usual hassles of OSS. Which means what it really needs is to be taken over by an actual business organization, with a team of developers and professional project managers and customer support people etc so no one person gets too burnt out and if anyone does, they have plenty of backup.