Pour the chicken broth (or water/pineapple juice) into the Instant Pot and add the salsa, minced garlic, chopped jalapeño, salt, black pepper, onion powder, Italian seasoning, and red pepper flakes (if using). Stir to combine.
Add the chicken breasts to the pot, ensuring they are at least partially submerged in the liquid.
Seal the Instant Pot and cook on high pressure for 10–12 minutes for fresh chicken or 12–15 minutes for frozen breasts, then allow a natural release for 5–10 minutes before quick-releasing any remaining pressure.
Use tongs to transfer the cooked chicken to a bowl or cutting board, reserving some of the cooking liquid in the pot.
Shred the chicken with two forks or cut it into pieces, then return some of the reserved cooking liquid to the shredded chicken to keep it moist and flavorful.
Stir in the lime zest and lime juice, taste and adjust seasoning if needed, then serve the chicken on tortillas or as desired with avocado, cilantro, and cheese.