I am fortunately logged into the forum now. Just a few minutes ago, there were dozens of different error messages during the whole signup process. Each step produced JS toast errors, or infinite loops, or bare JSON error documents. I've given up on Google SSO for now and am using username & password credentials.
I was worried I'd never login, which is a problem because the contact page doesn't appear to offer an unauthenticated way to report forum bugs.
Google SSO kept timing out. And the MFA setup timed out. But I'm in! Happy to be in! Anyone else seeing similar problems when setting up a fresh Arduino account? I wonder when the registration system will stabilize.