There is a whole line of Gazeteer products from 2e that detail a number of different lands. Their quality varies (IMO) but you might find something you like, The whole line (I think, at least) is available on www.dmsguild.com.
I like to add some mechanical flair to languages myself. I will often give Advantage if a characters shows they have learned the native language of whomever they are persuading. On the flip side, some NPCs may be so xenophobic that using Common around them is enough to be a Disadvantage.
The...