Did anyone else that gets regular email from the Social Security Administratipon/U.S. Treasury get one of these messages?

This doesn't sound concerning at all:

"Note: To activate the account, you enter willingly into an agreement with Robinhood Securities, LLC, which serves as the trustee for accounts <named after Grifter in Chief>"

Back in March/April, my accountant told me about the new accounts. She said no one knew many details yet and that I should expect an email with more information soon.