Place pork cubes and onion in a 6-quart slow cooker. Whisk vinegar, ketchup, brown sugar, pineapple juice, broth, soy sauce and ginger and pour over the meat.
Cover and cook on low for about 5 1/2 hours until the pork is nearly fork-tender. Add bell peppers and pineapple chunks, cover and cook on high for 30 to 45 minutes until peppers soften and pork is fully tender and at least 145°F, usually nearer 190°F for shoulder.
Lift pork, peppers and pineapple gently into a serving bowl with a slotted spoon. Pour cooking liquid into a saucepan, skim fat and simmer for 5 to 8 minutes until reduced to about 1 1/2 cups.
Mix cornstarch with cold water and whisk into the simmering sauce for 2 minutes until glossy and thick enough to coat a spoon.
Fold the hot sauce gently through the pork, peppers and pineapple without shredding the meat. Let stand for 3 minutes and serve.