How do I legitimately convert millions to fiat from wallet I found?

Say I go to a garage sale or found a wallet containing millions, what would be the best way to offramp it to fiat?

I know the usual process of off ramp is transfer to a CEX, sell and convert to fiat back to bank account. But if my account traditionally only off ramp hundreds of dollars and suddenly process say a million dollars, will they freeze my account?

Even if we get pass the CEX, as far as I know, at least where I'm from, banks will not accept millions of dollars from crypto exchanges without proper Kyc and source of wealth, and finding a hardware wallet does not exactly seemed like a legitimate way to establish one's source of wealth? How could I prove that I really found the wallet and what if the BTC inside is from illicit activities? Would I be implicated?