In a large bowl, combine pineapple, mango, lime juice, lime zest, tomato, onion, avocado, cilantro, mint, and salt. Refrigerate salsa covered at least 1 hour or up to overnight.
Pat chicken thighs dry with a paper towel. Season with salt and pepper.
Add water to the Instant Pot® and insert steam rack. Place steamer basket on the steam rack. Arrange thighs evenly in steamer basket. Lock lid.
Press the Manual or Pressure Cook button and adjust cook time to 7 minutes. When timer beeps, quick-release pressure until float valve drops and then unlock lid. Check chicken using a meat thermometer to ensure the internal temperature is at least 165°F.
Transfer chicken to eight plates. Garnish with salsa and serve.