Set a 6-quart or larger multi-cooker to the high Sauté setting. Add the chopped bacon and cook, stirring occasionally, until crisp, about 6-8 minutes. Use a slotted spoon to transfer the bacon to a paper towel-lined plate, leaving the rendered fat in the pot.
Add the chopped onion and bell pepper to the pot. Cook, stirring often, until softened, about 4-5 minutes. Add the ground beef and jalapeño (if using). Cook, breaking up the meat with a spoon, until the beef is browned, about 5-7 minutes. Ensure the beef reaches an internal temperature of 160°F (71°C). Carefully drain off any excess grease.
Stir in the minced garlic, chili powder, cumin, oregano, paprika, salt, and pepper. Cook for 1 minute until fragrant. Stir in the tomato paste and cook for another minute.
Pour in the beef stock, scraping the bottom of the pot to lift any browned bits. Stir in the Worcestershire sauce, undrained diced tomatoes, kidney beans, pinto beans, black beans, and about three-quarters of the cooked bacon.
Secure the lid, ensuring the steam-release valve is in the sealing position. Select the 'Chili' or 'Bean' setting, or use the 'Manual'/'Pressure Cook' setting on high pressure for 20 minutes.
Once the cooking cycle is complete, allow the pressure to release naturally for 10 minutes. After 10 minutes, carefully move the steam-release valve to the venting position to release any remaining steam.
Stir the chili well. If you prefer a thicker consistency, you can simmer it on the Sauté setting for a few more minutes. Taste and adjust seasoning if needed.
Ladle the chili into bowls and serve hot, garnished with sour cream, shredded cheese, cilantro, and the remaining crispy bacon.