There's no reason to leave your retirement account crypto - BTC, ETH, XRP - in anyone's control.
My introduction to virtual currency was through a checkbook control retirement account that I set up with ReSure (https://www.401kcheckbook.com/), a company that specializes in giving investors direct control over their IRA and 401k money. I use the same retirement account to invest in Bitcoin and real estate - for a very low flat fee. I get to keep in cold storage using a Trezor.