Bring 2 cups water to a boil. Add brine mix and stir until dissolved. Pour over ice in a flat bottomed resealable container. Add chicken, then add additional water until chicken is submerged. Brine for at least 5 hours or up to 12 hours.
Remove chicken from brine and rinse with cold water. Pat dry on a paper towel, then pound down the thicker end of the chicken breast until they are even thickness across.
Rub the chicken with 1 tsp olive oil until evenly coated. Season with salt, pepper, chili powder, and Oh My Spice! seasoning.
Air fry the chicken at 380 degrees for 11 minutes, flipping halfway through (sometimes I up the temp to 390 degrees after flipping the chicken for crispier edges). Set aside to cool for about 5 mintes before slicing thinly.
Whisk dressing ingredients and set aside.
Divide arugula between 4 serving dishes. Top with blackberries, pistachios, apple, sliced chicken, and dressing.
The sodium content displayed in the nutrition info here is estimated, since it will vary depending on how long you brine the chicken.