Place the chicken breast between two sheets of parchment paper and pound to an even half-inch thickness.
In a shallow bowl, whisk together the buttermilk with half of the smoked paprika and garlic powder.
Submerge the chicken in the buttermilk mixture and marinate in the refrigerator for at least 30 minutes.
In a separate shallow dish, combine the arrowroot powder with the remaining paprika, garlic powder, sea salt, and black pepper.
Remove the chicken from the buttermilk, letting excess drip off, and dredge thoroughly in the arrowroot mixture until fully coated.
Lightly brush or spray the coated chicken with avocado oil and place in the air fryer basket.
Air fry at 375°F for 12-15 minutes, flipping halfway through, until the exterior is golden and the internal temperature reaches 165°F.
While the chicken cooks, whisk the Greek yogurt and Dijon mustard together in a small bowl to create the sandwich spread.
Toast the sprouted grain bun until lightly browned.
Assemble the sandwich by spreading the yogurt sauce on the bun, then layering the lettuce, crispy chicken, and dill pickles.