In a small bowl, combine brown sugar, paprika, salt, pepper, garlic powder, onion powder, ground mustard, celery salt and cayenne pepper; mix well. Rub mixture over the entire surface of the rack of ribs.
Pour the broth or water into the Instant Pot and place trivet inside Instant Pot. Bend the ribs so that the ends are nearly touching and place in the IP on end.
Place the cover on the pot and set timer to 25 minutes on high pressure (pressure cook setting). It will take the IP around 12 minutes to build up pressure before it begins cooking.
When cooking time is done, let pressure release naturally for 10 minutes then do a Quick Release. Let the float valve drop and remove the cover.
Place the ribs on a baking sheet and brush the bbq sauce over the entire surface (both sides). At this point, either: 1. serve! or 2. Broil for 3 minutes per side and then serve!