RINSE corned beef under cold water. This removes the excess salt and brine.
PLACE your trivet inside the Instant Pot. Lay beef on top of trivet and sprinkle with seasoning packet. Sprinkle with minced garlic and lay sliced onion on top. Pour the beef broth on top.
SEAL Instant Pot and cook on High pressure for 90 minutes. When done, quick release the pressure (turning the valve to release pressure as soon as cooking time is done).
REMOVE beef and set aside. Cover with foil until you are ready to slice it. Remove Instant Pot trivet.
ADD sliced potatoes, carrots, and cabbage wedges into the Instant Pot and broth. Seal Instant Pot and cook on High for 3 minutes. Quick release and remove from broth. Broth can be removed and stored for a future soup.
SLICE corned beef against the grain into thin slices. Serve with cabbage wedges, carrots, and potatoes.