Others will start from either the Leather or Mail armor expert in Legendary Leathers in Dalaran.
Some quests will start from the Trainer and lead to other NPCs. I'm going to list each quest, where you get them, what you have to do, and the reward. Once you get your first quest, 'Skin Deep', you are ready to begin. It is recommended that you also have skinning, or at least a reliable way to get all the skins you need.Namha Moonwater will have the quest and be your main quest giver.Go to the Legendary Leathers shop in the Magus Commerce Exchange.You can start the Legion Leatherworking quests in Dalaran.
This guide will go over everything you need to know about Leatherworking in Legion including: I'm going to list all the Leatherworking quests, what you have to do, and more. There are many quests, they are available in different areas, and different times along the quest line.