Place the cubed potatoes in a large pot and cover with cold, salted water. Bring to a boil over high heat, then reduce heat and simmer until the potatoes are fork-tender, about 15-20 minutes. Do not overcook.

Drain the potatoes immediately and transfer them to a large bowl. Let them cool for about 10 minutes. While still slightly warm, gently toss the potatoes with the apple cider vinegar to allow them to absorb the tanginess.

While the potatoes cool, prepare the dressing: In a separate medium bowl, whisk together the mayonnaise, yellow mustard, sweet pickle relish, salt, and black pepper until smooth and well combined.

Gently fold the chopped hard-boiled eggs, celery, and red onion into the cooled potatoes.

Pour the prepared dressing over the potato mixture. Gently fold everything together until the potatoes and vegetables are evenly coated. Take care not to mash the potatoes too much.

Cover the bowl tightly with plastic wrap and refrigerate for at least 4 hours, or preferably overnight, to allow the flavors to meld. Before serving, taste and adjust seasoning (salt/pepper) if necessary, and garnish with a light sprinkle of paprika.