Login.gov is adding the capabilities needed to meet IRS’ identity and credential proofing requirements.

Will require biometrics in some form, with fallback to in person proofing at USPS.

I was absolutely flabbergasted that they didn't even white-label the third party stuff behind their own .gov domain, which means they're mis-training users towards "It's normal to hand over extremely sensitive official information to vaguely-plausible-looking companies with websites and certificates ultimately under the control of Montenegro."

And they'll accept anything from you without any ID whatsoever if you just use paper and a postage stamp.

What do you mean exactly?

The IRS doesnt require any auth if you print out whatever and mail it to them, no internet. They just believe you

I doubt any conventional web user knows or cares that “.me” is a ccTLD, or that it’s even related to Montenegro. If anything the reaction is “you don’t need a .com!?”

SSA Already announced the switch to login.gov, it looks like it will have broad support if they are starting the migration there.

I don't suppose this implies the end of the social security number as a form of identity access authorization?

No, because the government didn’t use it as one, just private businesses.