Season the Pork: In a small bowl, mix cumin, smoked paprika, oregano, salt, and pepper. Rub the mixture evenly over the pork shoulder.
Assemble in Slow Cooker: Place chopped onion and garlic at the bottom of the slow cooker. Add the seasoned pork shoulder on top. Pour in pineapple, chipotle peppers, apple cider vinegar, and brown sugar.
Cook: Cover and cook on low for 8-10 hours or on high for 5-6 hours, until the pork is tender and easily shreds with a fork.
Shred and Serve: Remove the pork, shred it, and return it to the slow cooker to mix with the sauce. Serve hot.