Season both sides of the chicken with the chili powder, cumin salt, and pepper and rub to coat.

Set the Instant Pot to SAUTE and add the oil. Once hot and shimmering, add the chicken breasts in a single layer. Sear on each side for 2-3 minutes, just until brown (the chicken does not need to be cooked through). Remove to a plate and set aside.

Turn the Instant Pot OFF. Splash the water into the pot and with a wooden spoon or rubber spatula, scrape up any stuck-on bits of food. Return the chicken to the pot, then pour a generous ½ cup of enchilada sauce over the top of the chicken.

Lock the lid in place. Cook on manual (high) pressure for 8 minutes. As soon as the time is up, vent immediately. Carefully open the lid. Check the chicken for doneness. It should register 165 degrees F on an instant read thermometer (if it is not done, reseal and cook an additional 1 to 2 minutes as needed). Remove the chicken to a plate.

Turn the Instant Pot to saute and bring the cooking liquid to a simmer. Let simmer until the liquid thickens and reduces by roughly half, about 5 minutes, stirring periodically.

Shred the chicken, either with two forks on the plate or place the whole breasts back into the Instant Pot after the sauce has thickened and use a hand mixer on low speed to shred it directly in the Instant Pot.

While the chicken cooks, prepare the tortillas. Place racks in the upper and lower thirds of your oven and preheat the oven to 350 degrees F. Divide the tortillas between two baking sheets, arranging them in a single layer. Brush the tops of the tortillas lightly with oil or spray with nonstick spray. Flip and repeat on the other sides. Bake on the upper and lower racks, just until the tortillas are warm and pliable, about 3 minutes. Stack the tortillas on a plate and cover with foil to keep warm.

Place the shredded chicken back into the Instant Pot and stir to coat with the sauce. Stir in half of the green onions, the Greek yogurt, and ¾ cup Monterey Jack cheese.

Spoon about ½ cup of the remaining enchilada sauce into a 9-by-13-inch baking dish and spread into a thin, even layer. Fill each tortilla with a heaping ¼ cup of the chicken filling, roll to close, then place it at one end of the pan, seam-side down. Repeat with the remaining tortillas, lining them down the pan as you go.

Pour the remaining 1 ¼ cups enchilada sauce over the top of the tortillas. Sprinkle with the remaining ¾ cup Monterey Jack cheese.

Bake the enchiladas until warmed through and the cheese is melted and bubbly, about 15 minutes. Sprinkle the remaining green onions over the top. Serve hot with desired toppings.