Place trivet in bottom of instant pot. Add onions, brisket, garlic, bay leaves, broth and brisket spice packet. Cook on high pressure for 75 minutes and natural release for 15 minutes. Open pot and remove meat to platter to rest. Cut potatoes and peeled carrots into large chunks and add to pot. Add cabbage on top and cook on high 4-5 minutes, then quick release. Slice corned beef and serve with vegetables.