Is it going under the mattress? Maybe Treasury bonds and bills.
I bought Series I bonds and TBills last week. My wife also bought a Series I bond. I moved it all out of my Citizens Bank account.
Most likely into treasuries. Take the risk off. Maybe you buy a 1 year T-Bill (or shorter duration and roll it over, or a 2 year) and take the 3.5% give or take. You may end up losing 3% from inflation but there is no other market risk, there is no bank collapse risk etc.
One thing to look at is stock market inflows and outflows. I doubt much of the cash is going into the stock market but it would be one way to narrow guesses. Bond yields have gone generally down the last few weeks, which suggests money has been moving into them.
We withdrew large amounts and put it into real estate. You can only fit so much under a mattress. Some is in vacuum-sealed bags hidden away.
Our fear is the Feds going to digital currency and then invalidating paper money. So some is in silver and gold, but even that is a gamble. We are all being screwed as financials collapse.