Kind of shocked this isn't a thing on top of current homebrews. That's actually a Ranger feature called Natural Explorer, Rangers gain double proficiency on a favored terrain.
D&D Beyond RangerTruthfully IMO Ranger is to much homebrewed and the changes cover up what was actually the ranger class. Currently they are able to get more skills than a Rogue via the new class choices. While getting a mix match of other classes thrown into there own and removing core features that made the class what it was years ago (at least in 3.0, Favored Enemy?).
This was mentioned in a previous post.
Bounded Accuracy