In the Instant Pot, place onion, carrots, celery, garlic, lentils, tomatoes, thyme, Italian seasoning, salt or salt substitute, pepper and broth. 

Stir to combine.

Set Instant Pot to Pressure Cook (Manual, High) for 18 minutes. If lentils are presoaked (recommended), you can reduce cooking time to nine minutes.

Allow soup to naturally release its pressure and enjoy. (This takes about 20 minutes.)

Add spinach when ready to serve. If your kids are not ready for green things floating around in their soup, you can just put them in your individual bowls and they will wilt on contact, leaving most of their enzymes intact.

Sauté onion in water until slightly softened. 

Add garlic and cook until fragrant.

Add carrots and celery for a few more minutes. 

Add other ingredients (except spinach) and bring to a boil. 

Simmer on low until lentils and vegetables are soft.

Add spinach when ready to serve.