Lol, these comments...

So here's the deal. An IRA can invest in almost anything except collectibles. See https://www.irs.gov/retirement-plans/retirement-plans-faqs-regarding-iras-investments So you can buy, stocks, bonds, crypto, real estate, businesses, etc.

BUT!

The vast majority of IRAs are set up with traditional brokerage houses like BAML, TD Ameritrade, etc. Those are the ones with low fees.

So you could open/rollover your IRA at a brokerage and buy your stocks, bonds, ETFs, foreign stocks (or at least their ADRs). So far though, I don't think any bitcoin ETFs have made it through the regulatory hurdles to get listed. I know I saw a headline that Bloomberg wants to bring one to market, so that may be a possibility somewhat soon.

There's also the news that the NASDAQ is looking into crypto, so that may be a possibility in the short to medium term future as well.

If you want your IRA to hold cryptos directly, then you are talking about an IRA not held at a brokerage account. These are called self-directed IRAs. But these violate your low fees rule. Typically the administrators charge something like 2% of assets under management (AUM). But you can really buy anything. A common strategy is to open an LLC opened by your IRA so you can then hold title to things in the LLC's name rather than the IRA's name. It makes for smoother transactions that way since people get all weird when you try to buy something in an IRA's name.

Another issue with self-directed IRAs is that you can't do anything yourself. This is to prevent self-dealing which is a giant no-no from the IRS. The point of the IRA (and all qualified funds like 401ks, 403bs, etc) is that the money is set aside for the future and you have not taken possession of the funds. That's why there's a tax deferral on it. So in order to do any transactions in the self-directed IRA you have to tell the administrator to do it for you. Those extra steps are, in my opinion, super annoying, take a lot of time, and cause those higher fees.

But if you want to investigate self-directed IRAs, there are a bunch of administrators out there. One that I used to have dealings with was https://www.trustetc.com/ - this isn't an endorsement, just letting you know they exist.

Hope that helps.