Sprinkle short ribs with salt and pepper.

Add oil to 6 Quart Instant Pot and select high Sauté setting. Allow oil to heat for 2 minutes. Transfer half of ribs to pot and cook 8 to 10 minutes or until browned, flipping once. Transfer ribs to plate. Repeat process with remaining ribs.

Drain all but 1 tablespoon fat from pot. Add onion to pot and sauté 3 to 4 minutes or until onion is softened, stirring occasionally. Stir in thyme, garlic, apples, raisins, broth, vinegar and brown sugar. Return ribs and any accumulated juices on plate to pot.

Secure Instant Pot lid and set Pressure Release to Sealing. Press Cancel button to reset cooking program. Select Meat/Stew setting and set cooking time for 35 minutes at high pressure (pot will take about 5 minutes to come to pressure before cooking time begins).

When cooking time ends, let pressure release naturally for 10 minutes, then move Pressure Release to Venting to release remaining steam. Open pot and transfer ribs to serving dish and cover to keep warm.

Skim fat from liquid remaining in pot. Press Cancel button to reset cooking program. Select high Sauté setting and allow cooking liquid and apple mixture to reduce for 8 to 10 minutes or until thickened. Ladle cooking liquid over ribs and serve immediately.