In a small bowl, whisk together oregano, cumin, achiote paste, chile powder, onion, garlic, lime juice, orange juice, and beer until combined.
Cut the pork into large pieces, removing any large chunks of fat. Season pork chunks with salt and pepper.
Heat a large fry pan over medium high heat. Add olive oil. When oil is shimmering, add half of the pieces of pork. Sear on both sides and remove to a plate. Repeat with the rest of the pork. Or Set Instant Pot to Sauté. Add olive oil. Once hot, add half the pork and sear directly in the Instant Pot, turning every 45 to 60 seconds. Transfer pork to a separate plate and repeat with remaining pork pieces until browned. Press cancel to turn off the heat. (I find it easier to sear stove-top)
Place brown pieces of pork into the instant pot. Pour sauce on top of the pork. Close lid and set to pressure on high. Cook for 25 minutes. Let naturally release for about 15 minutes. Release the remaining steam before removing lid.
Remove pork to a large cutting board and when cool enough to handle, shred with two forks. Spread pork onto a large baking sheet. Spoon one third of the sauce from the Instant Pot on top of the pork, tossing to combine.
Set broiler temperature to 550. Broil for 4 to 5 minutes, until the pork edges begin to crisp.
Remove the baking sheet from the oven and top with half of the remaining sauce in the Instant Pot. Toss again to combine. Broil for an additional 5 minutes.
Remove the baking sheet from the oven and toss more sauce. Don't use too much sauce. You don't want that pork to be swimming.
To assemble the tacos, top warmed flour or corn tortillas with pork. Top with sliced red onion, diced avocado, jalapeno, cilantro, pickled onions, or diced sweet onions and cotija cheese. Serve with lime wedges.