While it’s not being run by D&D rules my current campaign setting could fit the bill well enough.

Funnily enough, the party’s desire to explore fantastical wilderness has led them into few scenarios that question the literacy of common folk. As things go I don’t see the need existing in most societies for every individual to be literate. Duervna is without a doubt the most literate nation that bothers to interact with the rest of the world. They’re rather fond of putting magic runes on most everything and their magical prowess has been applied to agriculture yielding more leisure time for the average citizen. Given their magic is mostly region limited they haven’t exported their culture all that much.

Dwarves have higher literacy as expected given the prevalence of trade in their cultures. The same can be said to a greater extent for the Lengi, straightforward speaking four armed gorilla people who have a ‘challenge accepted’ mindset when it comes to most tasks, trade included.

Beyond that? Most people just know enough to do what they do, generally bits and pieces related to trade.