https://forgottenrealms.fandom.com/wiki/Helm (A god who killed Mystra once, badly damaging the weave and creating wild magic and dead magic zones, lovingly known as Helmlands. I hope we encounter a few of those in our adventures, if only to make things more interesting)
Wouldn't we more than likely see the leftovers from the spellplague? I know there is still cave-ins from underdark areas because of it along with broken portals and messed up locations still not healed.
Edit* I might be mixing stuff up : /
There are still some out there but during the spellplague, Mystra hid her power inside Elminister's body (which why he didn't go mad) and, as part of her resurrection, E used that power to repair the plagued areas. (WotC's message to DMs, we're not saying you can't use that if you like but we're no longer focusing on it)
Given that wild magic is now one of the core sorcerer classes I think wild magic areas are probably fairly common.
