login.gov is the government's (quite fantastic) auth flow - id.me is a private one that the IRS contracted. I wish there were a rule that all online government services needed to use login.gov, but alas it's optional.
They’re supposedly working on it [1] but I don’t have any sense of whether they’re likely to succeed. In particular, the IRS is beginning to onboard to login.gov and the goal is to be fully migrated away from ID.me at some point.
