Preheat oven to 375° Fahrenheit. If needed, adjust oven racks to center of oven.
Liberally season chicken thighs with salt and freshly cracked black pepper, then flip thighs over and season other side. Set chicken thighs aside.
Heat large cast-iron skillet over medium heat. When skillet is warm, add neutral oil and swirl pan to coat bottom with oil. Heat oil over medium heat until hot and shimmering.
When oil is ready, place chicken thighs in hot skillet, skin-side down. Sear chicken 3 to 5 minutes or until skins begin to brown and crisp.
Carefully flip chicken thighs over and sear other side 3 to 4 minutes until browned. Transfer seared chicken thighs to plate and set aside. Do not drain skillet.
Add Italian sausage links to skillet. Cook 2 to 4 minutes or until sausages begin to brown.
Flip sausages and cook other side 2 to 4 minutes until browned. Transfer browned sausages to plate with chicken thighs and set aside. Do not drain skillet. Note: sausages likely won't be cooked through completely at this point. That's fine. If skillet begins to smoke while cooking sausages, reduce heat as needed.
Add sliced onion, sliced bell pepper, chopped sage, chopped rosemary, and chopped garlic to skillet. Cook, stirring occasionally, until onions and peppers are tender, approximately 8 minutes. Note: if ingredients begin to burn, reduce heat as needed.
When onions and peppers are tender, pour in white wine to deglaze skillet. Use spatula to scrape up any browned bits of food that may be stuck to bottom of skillet. Let mixture cook 7 minutes or until wine has reduced by approximately 50%.
Once liquid has reduced, add peppers, pepper brine, and chicken broth to skillet. Gently stir to incorporate ingredients, then let mixture cook 5 minutes until liquids are heated through.
If desired, slice sausage links into 3 to 4 pieces each. Return chicken thighs and sausages to skillet and spoon liquid over top of proteins.
Place skillet in preheated oven. Bake dish 30 minutes, or until chicken thighs reach 160° Fahrenheit internally. Remove skillet from oven and let rest 5 minutes.
Divide chicken scarpariello evenly onto serving plates with desired side. Top with chopped fresh parsley if desired and serve warm.