Read through the SVB news, just learned that FDIC only protects up to $250k cash for you in each bank. So just a naive thinking: is there any sort-of aggregation service existing to help automatically spread your $10M fat wallet into 40 banks, and auto-withdraw if you need more than $250k.
I don't think super-rich will need this though.
Besides what nvader mentioned, a government money market fund from a big managers such as Vanguard or Fidelity should be safe. You can also buy Treasury bills and bonds directly from the government through TreasuryDirect.
Back when Merrill Lynch was a full-service broker and CDs paid enough interest that you'd care, your broker could look up CDs offered by various banks and also a secondary market of CDs that people wanted to sell and you could invest money FDIC insured that way.
Yep, this exists. Look for IntraFI or MaxSafe.
In more detail in this article: https://www.nerdwallet.com/article/banking/how-to-insure-you...