In a large pot, add potatoes and fill with water to cover by an inch or two. Bring to a boil over high heat and add 1 tablespoon of salt. Lower to a gentle boil and cook until potatoes are tender when pierced with a knife, about 25 minutes. Remove potatoes with tongs and set aside to cool.
When the potatoes have cooled slightly, peel potatoes and cut into 1-inch dice while still warm. Add to a large bowl, drizzle with apple cider vinegar, and set aside.
In a small pan, add eggs and cover with water by an inch. Bring to a boil over medium-high heat, then turn off heat, cover and let stand for 13 minutes. Immediately dunk the eggs into a bowl filled with cold water. Once cold, peel the eggs and chop into a ¼ inch dice (or use a pastry blender to crush the eggs in a small bowl).
Combine diced eggs, mayonnaise, dry mustard, Dijon mustard, black pepper, and 1-1/2 teaspoons salt in a bowl. Add in diced celery, onion, and bell pepper. Add mixture to the bowl of potatoes and toss gently to combine. Sprinkle green onions on top.
Refrigerate for at least 30 minutes or up to 24 hours before serving.