In a large pot, heat the olive oil over medium heat. Add the diced onion and cook until translucent, about 5 minutes.
Stir in the minced garlic, green bell peppers, carrots, and celery. Sauté for another 5-7 minutes until the vegetables start to soften.
Add the chopped cabbage and tomatoes to the pot, stirring well to combine with the other vegetables.
Pour in the vegetable or chicken broth and bring the mixture to a boil. Reduce the heat to a simmer and add salt, black pepper, paprika, thyme, and basil.
Cover the pot and let the soup simmer for about 30-40 minutes, or until all the vegetables are tender. Stir occasionally to prevent sticking.
Taste the soup and adjust the seasoning with additional salt and pepper if needed. If using, sprinkle in the chili flakes for added heat.
Serve hot, garnished with fresh herbs if desired, and enjoy your nourishing cabbage soup.