Put the potatoes in a medium saucepan, cover with water, and bring to a boil over medium-high heat. Decrease the heat to medium, cover, and cook until the potatoes are just tender, about 15 minutes. Drain and let cool.
Scoop the avocado flesh into a large bowl and mash with a fork. Add the vinegar, dill, lemon juice, mustard, and pepper and stir until evenly distributed. Add the pickles