Turn on a multi-functional pressure cooker (such as Instant Pot(R)) and select Saute function. Pour oil into the pot. Add onion and cook until softened and translucent, about 5 minutes. Add chicken; cook and stir until nearly browned, 3 to 5 minutes.
Stir in sweet potato, mushrooms, and celery, followed by tomatoes, tomato sauce, broth, chili powder, cumin, mustard seeds, garlic powder, salt, and pepper. Add whole jalapeno peppers. Close and lock the lid. Select low pressure according to manufacturer's instructions; set timer for 25 minutes. Allow 10 to 15 minutes for pressure to build.
Release pressure using the natural-release method according to manufacturer's instructions, 10 to 40 minutes.
