Select ‘Saute’ on the Instant Pot. Add oil to the bottom of the pot. When it starts to shimmer, add half of the meat, season the beef cubes with a little salt and pepper, and cook until browned. Flip and repeat until browned on all sides.
Transfer meat to a plate and repeat with remaining oil and beef. Press ‘Cancel’ when the second half of the meat has been browned. Return all meat to the Instant Pot.
Add the onion, potatoes, carrots, celery, garlic, diced tomatoes, beef broth, thyme, and Italian seasoning to the Instant Pot. Stir, lock the lid into place, set the vent valve to the ‘sealing’ position, and cook on high pressure.
Allow for 10 minutes of natural release before flipping the value to the ‘venting’ position to release any remaining pressure. Press ‘Cancel’ then select the ‘Saute’ setting.