Add the chopped onion to the pot and cook until softened, about 3 minutes. Add the minced garlic and cook for 1 minute more until fragrant. Press Cancel.
Add the chopped cabbage, chicken broth, diced tomatoes, Italian seasoning, salt, pepper, and bay leaf to the Instant Pot liner. Stir everything together briefly.
Place the browned sausage back on top of the vegetables; do not stir it in completely.
Secure the lid and set the vent to Sealing. Select Manual or Pressure Cook (High Pressure) for 5 minutes.
When the cooking cycle finishes, allow a Natural Pressure Release (NPR) for 10 minutes. After 10 minutes, carefully move the vent to Venting to release any remaining pressure (Quick Release).
Remove and discard the bay leaf. Stir the soup well before serving.
Notes
For a low-carb option, skip adding potatoes or rice.