Sauté bacon in large pot over medium heat until crisp. Transfer to paper towels to drain. Add onion to drippings in pot; increase heat to medium-high and sauté until beginning to brown, about 7 minutes. Add garlic and thyme; stir 1 minute. Add tomatoes with juice. Stir until almost all liquid evaporates, about 2 minutes. Add all potatoes; stir to coat. Add 4 cups broth; bring to boil. Reduce heat to medium-low, cover with lid slightly ajar. Simmer until potatoes are tender, stirring occasionally, 10 to 12 minutes. Add spinach and bacon; stir until spinach wilts, about 1 minute, adding broth by 1/2 cupfuls if too thick. Season with salt and pepper.