Pat chicken thighs completely dry with paper towels - this is crucial for crispy skin. Rub with 1/2 tablespoon olive oil, then season all over with 1/2 teaspoon salt, pepper, and smoked paprika. Heat a large oven-safe skillet over medium-high heat. Place chicken skin-side down and sear without moving for 5-6 minutes until the skin releases easily and is deep golden brown. Flip and sear 2 minutes more. Transfer to a plate; the chicken will be raw inside.

Pour off all but 1 tablespoon of chicken fat from the pan. Add remaining 1/2 tablespoon olive oil and return to medium heat. Add onion and cook 4 minutes, stirring occasionally, until softened at the edges. Add garlic and cook 30 seconds until fragrant. Add eggplant and cook 5 minutes, stirring once or twice - it will absorb oil then release it as it softens.

Add zucchini and bell pepper. Cook 3 minutes, then add crushed tomatoes with their juices, remaining 1/2 teaspoon salt, and thyme sprigs. Stir to combine and bring to a gentle simmer. Let cook 5 minutes until the vegetables begin to soften and the sauce thickens slightly. Stir in red wine vinegar.

Preheat oven to 400F. Nestle the seared chicken thighs skin-side up into the vegetable mixture, ensuring the skin sits above the liquid to stay crisp. Transfer the skillet to the oven and bake 25-30 minutes until the chicken reaches 165F internally and the vegetables are tender. The skin should be crackling and the sauce bubbling at the edges.

Remove from oven and let rest 5 minutes. Discard thyme stems. Taste the ratatouille and adjust seasoning if needed. Serve directly from the skillet, spooning the vegetables and sauce alongside each chicken thigh. Garnish with fresh thyme leaves.