Set yogurt out so that it can come to room temperature.
Add broth, chicken, onion, garlic powder, salt, pepper, and Italian seasoning into Instant Pot.
Add the pasta. Cover with mushrooms, tomatoes and green peppers. Don’t stir. Pressure cook 3 minutes. Let pot sit for 5 minutes then vent. Remove the lid.
Turn off Instant Pot. Stir flour in with yogurt. Stir in some of the liquid from the pot to temper. Add pepperoni, yogurt, and cheese into the Instant Pot.