30 day treasury bills are a better option than Cds currently. Stagger 5k$ bills over 4 weeks. Each week after 30 days, you will get the interest accrued put into your account and you do not have to pay state income tax on the earnings.
OP, this advice and that of others related to a HYSAs sound the most solid to me personally. Short-term stuff that's easily exitable, that will at least keep the value of your cash from shrinking from inflation.
With something like one lump-sum right now, I'd personally avoid putting anything into real-estate, gold/silver, or the stock market/equities with everything at peak prices - all of these are cyclical, and we're at the peak of a cycle. It's a global and national asset bubble, that has about 10 different needles pointed at it with each threatening to pop it at any time. Stuff that historically over the last 200 years is around 10 or 15 to one PE ratio is 35 or 40 to one. With the only times you see these big PE spikes being peaks of cycles just before they crash. But will it be tomorrow, or 2027? Nobody knows. But - if you have a nice, accessible lump-sum on hand, you'll be able to buy chunks of the entire economy at firesale prices.
There's an old saying, IIRC from Warren Buffett, that goes something like "Time
in the market always beats
timing the market," but circumstances like these are about the only exception. You really don't want to put your emergency fund into anything long-term right now, or anything you couldn't easily cash out of. Buffett himself is sitting on the largest percentage of his company's value ever held in cash, right now - explicitly waiting for that firesale to hit.
Even today, the market's crashing about 2% alone based off some unexpected trade games out of China and the Administration's response - will it be a one-day thing, or will it trigger a further collapse of China's economy that could be globally contagious? Lots of stuff going on right now, at the peak of asset prices. Better to sit on that fund in a way that covers inflation and can be easily accessed for emergencies or opportunities as they arise.