Use the sauté setting on your instant pot to brown the ground beef. Set it to low and cook for about 5 minutes stirring frequently until all of the ground beef has browned. If you're using very lean ground beef you may need to add some oil to the pot. Once the meat has browned turn off the Instant pot.
Chop the onion, bell pepper and mushrooms into bite size pieces.
Add the onion, bell pepper and mushrooms to the pot and stir into the meat.
Add the remaining ingredients into the pot (4 cans of beans, 2 cans of diced tomatoes and chili seasoning mix). Stir all ingredients together. Be sure that the ingredients do not extend past the maximum fill line for pressure cooking.
Close the lid and then cook the chili using the pressure cook setting on high for 30 minutes.
Serve with toppings of your choice.