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1
Combine 8 cups water, beans, sage, and sliced garlic in large saucepan. Bring to boil; reduce heat to low, cover, and simmer until beans are tender, stirring occasionally and adding more water by 1/4 cupfuls to keep beans submerged, 2 to 2 1/2 hours, depending on age of beans. Add 1 teaspoon sea salt; simmer 10 minutes. Uncover and cool beans in liquid. DO AHEAD:
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2
Heat 3 tablespoons oil in large pot over medium heat. Add onion; sprinkle with sea salt. Cook until onion is translucent, stirring often, about 5 minutes. Add chopped garlic; stir 2 minutes. Add celery, carrot, potato, fennel, and thyme; cook until vegetables are tender and begin to turn brown in spots, stirring often, 15 to 18 minutes. Add kale, chard, cabbage, tomatoes, Parmesan rind, 5 cups water, and 1 teaspoon sea salt. Bring to boil; reduce heat to medium-low, cover, and simmer until vegetables are very tender, about 1 1/2 hours. Add beans with cooking liquid and crushed red pepper. Add 2 cups broth. Season with salt and generous amount of pepper. DO AHEAD:
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3
Rewarm before continuing.
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4
Add bread to soup and simmer, stirring often to break up bread into smaller pieces and adding more broth by 1/2 cupfuls to thin, if desired. Season with sea salt and pepper.
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5
Divide ribollita among bowls, drizzle with oil, and serve.
