Crisp the bacon in a large skillet over medium heat, 6–8 minutes. Transfer bacon to a plate.
Spoon off excess drippings, leaving about 1 tablespoon in the pan.
Sauté onion in the bacon fat until softened, 3–4 minutes. Stir in garlic and paprika for 30 seconds.
Add cabbage, salt, and black pepper. Toss to coat and cook, stirring often, 8–10 minutes until tender-crisp.
Stir in butter, vinegar, red pepper flakes, and brown sugar. Cook 1–2 minutes to meld flavors.
Return bacon to the skillet and toss. Taste and adjust seasoning. Serve hot.