The only classes not in the PHB are the Artificer from Eberron and the Blood Hunter from Critical Role. I've not played either, so no strong feelings on either one.
If I had my way, I'd just go ahead and incorporate every subclass from XGtE. If I had to pick one... Damn. There's just too many good ones in XGtE to ignore.
I guess Divine Soul Sorcerer, just cuz that's a character I'm building right now.
