Prep the pork. Pat the pork cubes dry with paper towels. Toss with 1 tablespoon oil, salt, pepper, garlic powder, onion powder, and 1 tablespoon cornstarch until evenly coated.
Preheat the air fryer. Heat to 390°F (200°C) for 3–5 minutes. Lightly oil the basket or use a perforated liner.
Air-fry the pork. Arrange pork in a single layer without crowding.
Cook 12–15 minutes, shaking halfway, until browned with some crispy edges and an internal temperature of 145°F. Work in batches if needed.
Air-fry the vegetables and pineapple. Toss peppers, onion, and pineapple with the remaining 1 tablespoon oil and a pinch of salt. Air-fry at 380°F for 6–8 minutes, shaking once, until lightly charred but still crisp-tender.
Make the sauce. In a saucepan, whisk pineapple juice, ketchup, vinegar, soy sauce, brown sugar, ginger, and garlic.
Bring to a simmer over medium heat, then stir in the cornstarch slurry. Cook 1–2 minutes until glossy and thick enough to coat a spoon. Adjust sweetness or tang to taste.
Combine into a stew. Add the cooked pork, peppers, onion, and pineapple to a large skillet or pot.
Pour in the sauce and toss gently over medium heat for 2–3 minutes until everything is coated and hot. Stir in sesame oil if using.
Serve. Spoon over rice, then garnish with scallions and sesame seeds. Taste and add a pinch of salt or a splash of vinegar if you want more brightness.