Mix flour, chili powder, paprika, cumin, adobo seasoning, and cayenne pepper in a large bowl. Add pork and toss until coated.
Melt butter in a large skillet over medium heat; fry pork in batches until browned on all sides, about 10 minutes. Transfer browned pork to a slow cooker.
Cook and stir onion and garlic in the same skillet until vegetables are fragrant, about 1 minute. Stir tomatoes, barbeque sauce, brown sugar, and hot sauce into onion mixture and simmer for 5 minutes. Pour sauce over pork.
Cook on low for 5 to 6 hours. Transfer pork to a plate and shred with 2 forks. Return pork to slow cooker and stir. Continue to cook, uncovered, until thickened, 10 to 15 minutes.