Does Elminster know anything about settings like Eberron, Ravnica, Exandria, or Theros?"Anything," yes. As in, not much.
It's safe to say that anything you or I know, from reading official published lorebooks, El knows, too.
Plus a little more covert stuff, involving cabals of beings who trade/travel between multiple planes/worlds.#Realmslore
— Ed Greenwood (@TheEdVerse) February 27, 2021