Cut the pork shoulder into four large pieces, working around the bone. Season the pork evenly with the salt, pepper, and cumin.
Turn the Instant Pot on the "saute" setting. When hot, add the olive oil and pork. Cook for about 4 minutes or until golden brown. Flip and cook for another 4 minutes or until the pork is evenly browned.
Add the onions, garlic, apple cider vinegar, and chicken broth. Hit "cancel" on the Instant Pot, then hit "manual" and increase the time to 90 minutes. Cover, seal, and cook.
When the cook time is done, press the “Keep Warm/Cancel” button to turn off the cooker and turn the valve from sealing to venting to release the pressure quickly.
When the pressure is released, carefully remove the lid. Use tongs to transfer the pork onto a cutting board. The pork should shred very easily by just squeezing it with the tongs or with two forks. Discard any unwanted fat and liquid.
Place the shredded pork in a cast-iron skillet set over medium-high heat and add the BBQ sauce over. Toss to coat and cook for about 5 minutes, or until the liquid is cooked off and the BBQ sauce has soaked into the pork. Season to taste with more salt, pepper, and BBQ sauce, if needed. Serve however you please and enjoy!