Measure olive oil into the inner pot and press SAUTÉ button to heat the olive oil. Once oil is hot (but not smoking), add onion, bell pepper, celery, salt, pepper, and red chili pepper flakes. Stir to combine; sauté for 4 minutes or until tender. Stir in garlic. Cook 1 minute, stirring often (to not burn the garlic).

Put dried beans and turkey into the pot. Pour in 4 cups of water, which should slightly submerge veggies and beans.

Lock the lid in place; flip Pressure Release knob to SEALING. Press the CANCEL button to stop the Sauté function. Select the MANUAL button (or the Bean/Chili or Pressure Cook button). Set cooking timer for 1 hour and 15 minutes at HIGH pressure. Once the Instant Pot has reached full pressure (takes about 15 minutes), the cooking time will begin.

Once cooking program has ended, let the pressure release NATURALLY for 25 minutes (do nothing!). After 25 minutes, flip the Pressure Release knob to VENTING, which lets any remaining steam escape. Once pressure gauge has dropped back down (indicating no remaining internal pressure), it is safe to open the Instant Pot.

Use a large slotted spoon (or tongs) to transfer turkey from the pot to a cutting board. Remove meat from the bones, discarding skin/bones. Cut turkey into small pieces (or shred it). Place meat back into the pot. Add apple cider vinegar; stir until incorporated. Taste soup; add more salt/pepper, if desired.

Serve soup immediately; garnish portions with cilantro or sour cream, if desired.