Boil the potato in salted water until tender, then drain and let cool before dicing into bite-sized cubes.
Hard-boil the egg, peel it, and chop it into small pieces.
In a large mixing bowl, whisk together the Greek yogurt, avocado oil mayonnaise, Dijon mustard, lemon juice, sea salt, and black pepper until smooth.
Add the diced potato, cooked chicken breast, chopped egg, red onion, celery, and fresh dill to the bowl.
Gently fold all ingredients together until everything is evenly coated in the creamy dressing.
Serve immediately or chill in the refrigerator for 30 minutes to allow the flavors to meld.