"Before Fidelity made its move, the Department of Labor had sent a warning about using crypto in retirement accounts. In March, the agency issued a compliance assistance release cautioning retirement plan fiduciaries to “exercise extreme care” when considering crypto currency investments." writes Mark Schoeff Jr. in Investment News.
“There is not an adviser who is not getting phone calls from plan sponsors about [using] crypto in plans,” said Keith Clark, managing partner at DWC The 401(k) Experts, a retirement plan compliance consultant. “No one has come out and said it is imprudent. But you read some of these comments, and you see it is a risk.”
You can read the entire Investment News article here in "Advisers caught between Fidelity, DOL on using crypto in 401(k)s"