Dry brisket and season generously with salt. Add grapeseed oil to pot and swirl to coat. When smoking, add brisket, in batches if necessary, and saute until deeply golden brown, about 5 minutes per side. Remove brisket to a plate as it finishes and replenish or drain oil as necessary to maintain approximately 2 tablespoons per batch. Add onion, garlic, ginger, jalapeno, cinnamon stick, and brown sugar, again replenishing pot if necessary with additional 1 tablespoon oil, and season generously with salt. Saute until onions are softened and golden in spots and brown sugar is caramelized, about 6 minutes more. Return brisket to pot, nestling meat beneath vegetables. Add vinegar, soy sauce, and beef broth, scraping bottom of pot to deglaze. (This can also be done in a skillet over high heat. Saute timing will be reduced. Transfer brisket, vegetables, and pan sauce to Instant Pot before proceeding.).
Top with lid and place on high pressure. Cook 45 minutes and then allow pressure to release naturally for 30 minutes. Uncover and remove brisket and vegetables with a slotted spoon. Cover with foil to keep warm. Transfer cooking liquid to a fat separator or measuring cup and skim fat. Return sauce to Instant Pot and place on saute setting. Bring to a boil and cook until reduced, 10 minutes. Add coconut milk and continue to reduce, 5 minutes more. Season to taste (the broth) with salt and lime juice. Return the meat and vegetables to the sauce and serve with rice, cilantro, and additional lime wedges.