Turn Instant pot onto saute function. Add the vegetable oil when display reads "hot". Add the onion, garlic, carrots, and celery, 1 tablespoon salt and 1/8 teaspoon black pepper.
Cook stirring frequently until the vegetables have slightly softened, about 4-5 minutes. Add 1 cup of water and stir, scraping up the brown bits on the bottom of the pan
Add 4 cups water and chicken flavor better than bouillon dissolved in water and mix. Add the chicken, turnip, carrots, garlic, bay leaves, and thyme.
Place the lid on and set the "steam release" knob to "sealing". Set to pressure cook on high for 20 minutes.
When the pressure cooking cycle has completed, allow it to sit, undisturbed, and completely depressurize for 10 minutes.
When the pressure cooking cycle has completed, set to "quick release" and wait until cycle has completed.
Carefully remove the lid (there may still be remaining steam). Remove the chicken and set aside to a large bowl until cool enough to handle.
Remove and discard turnip, garlic, bay leaves, and remaining thyme stems.
Set the Instant Pot to high saute and bring the soup to a boil. When at a boil, add the noodles and cook just until al dente, about 4-5 minutes.
Remove the skin and bones from the chicken and cut into chunks. Liberally season the chicken pieces with salt and pepper and return it to the soup. Adjust seasoning as needed and ladle into individual bowls and serve.