Set the Instant Pot to Sauté. Add 1 tablespoon olive oil , 2 onions, 3 celery ribs, 1 green pepper, and 2 cloves garlic. Cook for 3–5 minutes until softened.
Add 2 lbs ground beef , breaking it apart as it cooks. Drain excess fat if needed.
Stir in 20 ounces mushrooms, k19 ounces dark red kidney beans, 20 ounces tomato soup, d28 ounces diced tomatoes , 1 tablespoon chili powder, 1 teaspoon oregano , 1 teaspoon salt , ¼ teaspoon pepper , and 1 teaspoon sugar. Mix thoroughly.
Close lid, set valve to Sealing, and cook on Manual / Pressure Cook for 10 minutes.
Allow pressure to release naturally for 10 minutes, then carefully release remaining pressure.
Stir the chili and taste. Add remaining 1 tablespoon chili powder for extra heat if desired. Serve hot with optional toppings like shredded cheese, sour cream, or green onions.