Saute the Veggies. Set your Instant Pot to the sauté mode. Add a bit of oil, then toss in the diced onions, red and green bell peppers, and minced garlic. Sauté for a few minutes until the veggies start to soften.
Add the Chicken and Spices. Add the diced chicken pieces and the spices: chili powder, cumin, paprika, dried oregano, salt, and pepper. Stir well to coat the chicken and veggies with the spices.
Pour in the Tomatoes and Broth. Add the diced tomatoes (with their juices) and the chicken broth to the pot. Give it a good stir to combine everything.
Pressure Cook. Secure the Instant Pot lid and set it to the "Soup" setting or manual high pressure for 10 minutes. Allow natural pressure release for 5 minutes, then do a quick release.
Finish with Lime Juice. Stir in the fresh lime juice to brighten up the flavors.
Serve and Garnish. Ladle the chicken fajita soup into bowls. Garnish each serving with fresh cilantro, sliced jalapeños, shredded cheese, sour cream, and tortilla strips.