After the discussion with Stan, I remembered to file the 990-N for an organization I'm responsible for with a June year end.
I was able to find last year's credentials, but they no longer work.
Use the following URL for the 990-N filing site. It redirects.
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IRS had been threatening to force all taxpayers to identify themselves through ID.me but that hasn't happened yet. There is an option to create an account with Login.gov.
For the moment, Login.gov credentials are used with two IRS systems only, IRS Form 990-N (e-Postcard) and Qualified Intermediary Application and Account Management System (QAAMS).
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After submitting the 990-N, log out of both the 990-N filing site and Login.gov.
Past filing history was not preserved.