Use the saute mode on your Instant Pot or electric pressure cooker to heat the oil. Add the onion, beets, carrots and garlic. Allow to cook, stirring only occasionally, for about 10 minutes.
Add the potatoes, 1 quart of beef broth, and 1 tablespoon of kosher salt. Seal lid and cook on high pressure for 15 minutes.
Quick release pressure. If pressure cooker is big enough to accommodate cabbage and remaining beef broth, add now, seal lid, and cook on high pressure for 2 minutes. If not, transfer all ingredients from pressure cooker into large pot on stove, add cabbage and remaining broth, and bring to a boil. Cook just until cabbage softens.
Add red wine vinegar and fresh dill. Stir well and add salt and pepper, to taste. Borscht should be thick enough that it can nearly hold your spoon up, but there should be enough broth to make it resemble a soup. Serve each bowl with 2 tablespoons of sour cream.