macOS 10.14.4 Breaking Google Account Authentication for Some →

After upgrading my MacBook Pro to macOS 10.14.4 this morning, macOS has been asking me to re-authenticate the G Suite accounts I use in Mail.

For some background, I use Mail with one regular Gmail account and two G Suite accounts. Both of the latter asked to be logged back in, weirdly, hours apart:

Update: A few hours later, my regular Gmail account asked to be logged in again, too.

As pointed out by Greg Pierce, I am not the only one, and for some users, the problem is a lot worse than being asked to sign in again:

The issue puts me in an endless loop. I get a notification “Google requires completing authentication in Safari.” This takes me to a Sign in dialog where I enter email account and password. Password is correct and accepted, after which I’m back in the loop again asking to enter Google Password.

If I login to my Google account in Safari I can see the recent events that I signed in without any problems on this Mac, but Apple Mail does NOT connect and I am back in the endless loop.

Oddly I can add events to the Google Calendar for the account so apparently something is amiss strictly with Apple Mail.