Combine the cumin, salt, ancho chile powder, paprika and cayenne in a small bowl. Sprinkle over the pork, then drizzle on the oil and toss to coat. Set a 6-quart Instant Pot® to high saute and cook the pork in batches until all sides are golden brown, 3 to 4 minutes per side. Transfer the pork to a plate and set aside. Add the onions and cook until they begin to soften, about 2 minutes. Add the garlic and jalapeno and cook until fragrant, about 1 minute. Add the beer, orange juice and lime juice and stir to combine, making sure the pork is mostly submerged in the liquid. Select the cancel button on the pot.
Follow the manufacturer's guide for locking the lid and preparing to cook. Set to pressure cook on high for 30 minutes. After the pressure-cook cycle is complete, follow the manufacturer's guide for natural release. After 15 minutes, being careful of any remaining steam, unlock and remove the lid. The pork should be tender and cooked all the way through. Transfer the pork to a large bowl and shred with two forks.
Set the Instant Pot® to high saute and bring the liquid to a boil. Mix together the cornstarch and 1/4 cup water in a small bowl until smooth. While whisking, pour the cornstarch mixture into the boiling liquid. Let boil until slightly thickened, 2 more minutes. Press the cancel button.
Ladle the cooking liquid over the pork and season with salt, to taste. Serve with lime wedges, tortillas and desired toppings.
Pickled Shallots and Red Onions:
Combine the white vinegar, sugar and 1 teaspoon salt in a small saucepan with 1/2 cup water. Bring to a simmer over medium-high heat. Add the onions and shallots to a pint jar and pour the liquid over the top. Let cool completely. Refrigerate up to 1 week.