Begin by preparing all the vegetables. Chop the cabbage, onion, green bell peppers, tomatoes, carrots, and celery. Mince the garlic.
In a large pot, heat the olive oil over medium heat. Add the chopped onion and sauté for about 3-4 minutes until it begins to soften.
Add the green bell peppers, carrots, celery, and garlic to the pot. Cook for an additional 5 minutes, stirring occasionally.
Stir in the chopped tomatoes and cook for another 3 minutes.
Add the chopped cabbage and vegetable broth to the pot. Mix well.
Season the soup with thyme, black pepper, and salt.
Bring the mixture to a boil, then reduce the heat and let it simmer for about 20-25 minutes or until all the vegetables are tender.
Taste and adjust seasoning if necessary. Once ready, remove from heat.