Pat the short ribs dry with a paper towel and season all over with 2 teaspoons salt and 1 teaspoon pepper, using your hands to rub the seasoning all over the ribs. Transfer the seasoned ribs to a 6-quart or larger Instant Pot.
In a small bowl, stir together the soy sauce, sweetener, vinegar, sesame oil, garlic powder, red pepper flakes, and ginger. Pour the sauce over short ribs in the pot and toss everything together so the sauce reaches the bottom of the pot. Lock on the lid, turn the valve at the top to “sealing,” and program the Instant Pot to cook under high pressure for 35 minutes.
Let the pressure release naturally. If pressure hasn’t dropped after 25 minutes, release it manually by turning the top valve to the “venting” position. The ribs should be fall-off-the-bone fork-tender. If they’re not, cook for another 5 to 10 minutes under high pressure.
Use a slotted spoon to remove the ribs from the Instant Pot, transfer to a platter and tent with foil to keep warm. Discard any bones that fall away from the meat. Reserve 1/2 cup of the braising liquid and transfer the rest of the braising liquid to a saucepan and place over high heat. Reduce to a steady simmer and let the sauce reduce to about half, about 8 minutes. Taste the reduced sauce for seasoning, adjust if necessary with additional salt and pepper.
Meanwhile, braise the bok choy. Heat a large, wide skillet over medium-high heat, about 3 minutes. Add 1 tablespoon of the coconut oil. Add half of the bok choy, cut sides down and cook until browned, 3 to 4 minutes. Remove to a plate and repeat with the remaining oil and bok choy. Return all of the bok choy to the pan, seared sides down. Add reserved 1/2 cup of the braising sauce and bring to a boil. Reduce heat to medium-low, cover, and cook until the bok choy is very tender, 8 to10 minutes.
Spoon the reduced sauce over the ribs, and serve with the bok choy.