In the Instant Pot, combine the pork, onion, hominy and its juices (see Note), water, garlic, chipotle chiles, adobo sauce, ancho chile powder, cumin, oregano, and salt.
Secure the lid on the pot. Close the pressure-release valve. Select MANUAL or PRESSURE COOK and set the pot at HIGH pressure for 30 minutes. At the end of the cooking time, allow the pot to sit undisturbed until the pressure has released.
Check the pork for doneness. Taste and season with additional ancho chile powder and/or salt as needed. Garnish with the cilantro and serve.
Notes
NOTE: If you like your hominy more al dente, I suggest you put in half the can while cooking so it flavors and thickens the stew a bit, and save the other half to add after cooking.