Saute onion, celery, and carrots in oil in Instant Pot set to saute low until soft and starting to brown, about 5 minutes.
Add garlic and chili powder. Stir and cook 2 - 3 minutes.
Stir in tomatoes, stock, salt and pepper. Add chicken thighs and set Instant Pot to pressure cook on high pressure for 20 minutes.
Shred chicken and stir back into the soup.
To make tortilla strips
Preheat oven to 350 degrees and line a large baking sheet with parchment paper.
Place tortillas on the baking sheet in a single layer. Using a pizza cutter, cut the tortilla into ½-inch wide strips. Spray the top with avocado oil.
Bake until golden brown and crispy.
Serve the soup topped with tortilla strips, avocado slices, lime wedges, and fresh cilantro.
For a low carb, keto, and Whole30 option, skip the tortilla strips. Raw jicama sticks are a good substitute for crunch.*You can substitute plain diced tomatoes and add fresh diced jalapeno to taste. Saute the jalapeno with the vegetables in step 1.