
Place chopped potatoes in a large pot and cover with salted water. Bring to a boil and cook until fork-tender (about 8–10 minutes). Drain and let cool slightly.
In a large bowl, whisk together mayonnaise, mustard, apple cider vinegar, sugar, salt, and pepper until smooth and creamy.
Add the warm (not hot) potatoes to the bowl. Gently fold in celery, red onion, chopped eggs, and relish.
Stir until everything is evenly coated. Taste and adjust seasoning if needed. Cover and refrigerate for at least 2 hours (overnight is best).
Sprinkle with paprika before serving for that classic Southern look.