Place the cubed potatoes in a large pot and cover them with cold water. Add 1 teaspoon of salt.

Bring the water to a boil over high heat, then reduce heat to a simmer and cook until the potatoes are fork-tender, about 15-20 minutes. Drain completely and let them cool slightly (about 10 minutes).

While the potatoes cook, prepare the mix-ins. Cook bacon until crisp, drain on paper towels, and crumble. Set aside half of the bacon and half of the shredded cheddar for garnish.

In a large bowl, whisk together the mayonnaise, sour cream, buttermilk, Dijon mustard, apple cider vinegar, garlic powder, salt, and pepper until smooth and well combined. Taste and adjust seasonings if necessary.

Gently fold the warm, slightly cooled potatoes into the dressing. Be careful not to mash them too much—you want some texture.

Fold in the reserved bacon (half of the total), half of the cheddar cheese, and half of the sliced scallions. Gently mix until everything is evenly distributed.

Cover the potato salad and refrigerate for at least 2 hours to allow the flavors to meld. Before serving, garnish the top generously with the reserved crumbled bacon, cheddar cheese, and fresh scallions.