(Mojave) Apple Mail can't create Google mail-account – Safari 13.0 (14608.1.49) doesn't open anymore
Google Mail now obviously uses OpenID for authentication, so it must open a Safari page to allow you to authenticate. But – as of the most recent Safari update, I think – that window doesn't open. So, I can't re-enter the password for a GMail account, nor define a new one in the Mail application.
This is brand new behavior which seems to have begun with the most recent Safari update ... unless Google is also doing something weird(er) on their side. (Imagine that ...)