Set Instant Pot to Sauté mode. Once pot is warm, add avocado oil. Warm oil until hot and shimmery, then add ground beef, Italian sausage, chopped onion, minced garlic, and green bell pepper.
Cook, stirring periodically, until meat is browned and crumbled and vegetables are tender, approximately 5 to 7 minutes.
Drain grease from Instant Pot insert and return insert to Instant Pot. Add crushed tomatoes, tomato sauce, and tomato paste. Stir to incorporate, making sure to scrape up any browned bits that may be stuck to bottom of Instant Pot.
Add bay leaf, dried oregano, dried basil, salt, and pepper to Instant Pot. Stir well to incorporate spices.
Secure lid on Instant Pot and set valve to sealing position. Set Instant Pot to Manual High Pressure for 7 minutes. Instant Pot will pressurize and then cook time will begin.
When cook time ends, immediately (and carefully) Quick Release pressure. Once steam is completely released, carefully remove lid.
Remove bay leaf and discard. Stir in grated parmesan, then taste sauce and adjust salt and pepper as desired.
Once pasta is cooked, immediately transfer spaghetti noodles from pot of water (without draining) and into Instant Pot. Stir well to toss pasta with sauce, then let pasta and sauce cook together 1 to 2 minutes.
Divide pasta and sauce into serving bowls or onto plates. Top with additional grated parmesan if desired and serve warm.