Note: "OP" is in reference to the GP/original poster of this "Ask HN."
The greatest irony is that everything that was beaten into your unconscious mind as to what you "should do," and all the ways you learned to seek out human connection: all go out the window when you get a massive windfall.
The greatest two "shapes" our culture warps our spirits into are: a need for money (for its own sake) or a need for recognition (preftige) -- once the basic material necessities have been acquired (viz. stability of income and mind, reliable shelter and food, routine sleep, etc.). None of this is relevant anymore. You don't care what anyone else thinks about you, because you're completely self-sufficient. Just dump all your money into a balanced portfolio, and live off the income generated a la dividends and interest for the rest of your life. You no longer need anyone to satisfy physical needs. No boss to placate, no spouse to manage, and no "bridges" to tend.
Similarly, it becomes impossible to socialize with the majority of people. The things that their minds focus on, the habits they have, the lives they live are completely unrelatable when you have enough money to never doing anything again (yes, €7m is enough, if you're not a degenerate or foolish). It's like you're both from different planets, speaking completely alien languages, and unable to ever really understand one another. This assumes you'll find anyone truly interested in genuine socialization for pleasure alone; because as soon as those who still need to carry out the "daily toil" find out about your NW, the agendas come out in full force. You'll find that no, you never really had friends (or family). You simply had associates with mutual interests -- a give and take, transactional relationship was all that connected you.
OP, the only reason you were driven to do all those things was because you wanted to climb the social hierarchy. You saw your fellow apes with more money, more brains, and more status, and just like all those chimps before you, you thought "I need that. I gotta keep up. If I don't, I'm worthless. A loser, and no one will like me. I won't feel good about myself." But that's just an evolutionary trick nature pulled on us, because more-often-than-not animals with deep social hierarchies survived and reproduced more than those without. Once you've escaped the gravitational pull (see: the need to "fit" into a tribe in order to survive), you'll find that it was a scam all along. That all this shit around you exists to keep you busy so you don't start thinking too much about things, and can carry out your genetic directives (usually to the benefit of others), and then die.
The tragedy with you, OP, is that you're a young kid who never had to train his nervous system to become another "robot" that could continue successfully functioning in his society, until he became a corpse. You didn't work for that money, and so your spirit was never molded into the two most-successful "shapes": a need for more money, or a need for more prestige -- as you see with people that once started out with little, but forced themselves to work towards more (even when they're in the top 1% in either, they'll still keep going after more, because that's how they've molded themselves: to be a machine stuck in a loop -- coincidentally, staving off depression and other such "meaninglessness.").
You're basically on the same level as a trust-fund baby. What exactly do you do besides indulge in hedonism? If you're one of the aforementioned "keep on chugging," work-robots (an evolutionary-fit path) that have trained themselves to keep busy, then creative pursuits, investments, a new business venture, or non-profit/charitable work is what's in the cards. But OP isn't. Those things will never be satisfactory for him (remind me in 10 years).
All that's left for the modern nouveau nobleman's son is hedonism -- spending away all that money on pleasure-pursuits (drugs, sex, expensive items) just to feel something at all. If he was raised middle class, he'll probably still have the ingrained "shame" about such things, and will instead focus on more sedentary (see: "boring") habits, slowly wasting away. But if he was raised lower class, then he'll most likely fall into hedonism, the same as the accidents of the upper class.
That's the truth: OP's life will be aimless, because he doesn't have decades of experience "aiming" at something, and going after it.
The only thing left is that, in a time long ago, aristocrats would send their sons off to learn the classics, and get an "education," so that they wouldn't become flagrant hedonists, wanton raping, murdering, and making an all-around mess of things; instead their energies would be pushed in other, more "acceptable" directions, decided by pedagogists.
TL;DR OP: May I recommend dropping out of the sciences and other "hard" or niche topics? Go study with the ivory-tower academicians in a field you are actually interested in. Perhaps look into philosophy, or other "soft" topics, where nothing ever gets "done," and you can burn through the rest of your time on this earth, forever "working" on it. Maybe even go learn Ancient Greek, and see if you can rekindle some sort of greater humanity within yourself (doubtful, if that's not where your values lie).
Whatever it is, you will not find any meaning. Even if you decide to throw away all that money to be "rid" of it, you're forever a changed person -- and you can never go back. Find some tolerable pursuits that keep you busy, and don't leave you much time to think and ruminate. Something pleasurable, but not devilishly indulgent. Something sustainable.