So the solution seems to be to remove an old Google Account that was configured with a(n application-specific) password and add a new one with OAuth2 using your regular password (+ phone code) and allowing Ubuntu to access your account.
So the solution seems to be to remove an old Google Account that was configured with a(n application- specific) password and add a new one with OAuth2 using your regular password (+ phone code) and allowing Ubuntu to access your account.