Brown linguica in a large stock pot over medium heat. Dust duck breast with flour and add to pot, a few pieces at a time, until browned. Add onion, garlic, celery and carrot and cook for 5 minutes, stirring often. Add beef broth and wine, bring to a boil. Reduce heat, cover and simmer for 30 minutes. Add potatoes and diced tomatoes and simmer for 20 – 25 minutes more or until potatoes are soft. Season with salt and pepper.