In a large pot or Dutch oven, cook the Irish bacon over medium heat until crispy. Remove the bacon with a slotted spoon and set aside, leaving the rendered fat in the pot.
Add the chopped onion, carrots, and celery to the pot. Sauté until softened, about 5-7 minutes.
Stir in the chopped cabbage, chicken broth, dried thyme, and black pepper. Bring the soup to a boil.
Reduce the heat to low, cover, and simmer for 30-35 minutes, or until the cabbage is tender.
Season the soup with salt to taste. Return the cooked bacon to the pot just before serving.
Notes
Serve hot with crusty bread. This soup can be made ahead of time and reheats well.