Skipping past the obvious of paying off debts and buying a decent house, I'd do this:

Found a company to sell tech products (Pinephone, but cooler). Only the best benefits, work environment, basically everything I hate about any job I've worked, fixed. I'd hire good people, and make damn sure they're treated well. After everything is going well and with some kind of charter so they can't decide to be evil, I'd turn the company over to my employees. I'd step down and become a janitor or something and work ~20 hours a week until I retire.

Whatever money's left over, if there is any, is given away.

I want to work. I like working. I just want to work somewhere good, ya know?

I'd just buy my employer but they made ~450m Euro after taxes so they might want more than a billion. Also fuck audits.