Brown the aromatics: Heat the olive oil (2 tablespoons) in a large skillet over medium heat. Add the diced onion (1 medium) and cook for 7–8 minutes, stirring occasionally, until softened and translucent. Stir in the minced garlic (1 tablespoon) and cook for about 30 seconds, just until fragrant.
Brown the beef: Add the ground beef (2 pounds), Morton kosher salt (2 teaspoons), black pepper (1 teaspoon), Italian seasoning (2 teaspoons), and sweet paprika (½ teaspoon). Cook, breaking up the meat with a wooden spoon, until it is nicely browned and beginning to develop deeper color in spots, about 8–10 minutes. Drain any excess grease.
Prepare the broth: In a small bowl or measuring cup, dissolve the Better Than Bouillon Beef Base (1 heaping tablespoon) in ½ cup boiling water, stirring until completely dissolved
Slow cook the soup: Transfer the beef mixture to a 6- to 7-quart slow cooker. Add the chopped bell peppers (3–4 large), brown sugar (2 tablespoons), tomato sauce (15 ounces), diced tomatoes with their juices (28 ounces), beef broth (32 ounces), dissolved Better Than Bouillon, and Worcestershire sauce (1 tablespoon). Stir well to combine. Cover and cook on LOW for 6–8 hours or HIGH for 3–4 hours, until the peppers are tender and the flavors have blended.
Add the rice: Stir the cooked rice (2 cups) into the soup during the last 15–20 minutes of cooking on HIGH, just until heated through.
Serve: Taste and adjust the seasoning with additional salt and pepper, if needed. Ladle the soup into bowls and serve hot.