The Snout of Omgar is a geographical region described briefly in Tomb of Annihilation.
Not much is revealed about the location or its inhabitants in that adventure, however. The Tortle Package is written for Dungeon Masters who want to know more about the Snout of Omgar.
This supplement also introduces a new playable character race, the tortle, and a new adventure location: Dangwaru, the Typhoon Palace. All of this is permissible for play within the D&D Adventurers League.