Heat the olive oil in a large pot or Dutch oven over medium-high heat. Add the sliced sausage and cook for about 5-7 minutes, until it's nicely browned. Remove the sausage from the pot and set it aside.
Add the chopped onion to the same pot and cook for about 5 minutes, until it's softened and translucent. Add the minced garlic and cook for another minute, until fragrant. Stir constantly, so the garlic doesn't burn.
Stir in the salt, pepper, smoked paprika, and red pepper flakes (if using). This helps to build flavor early on.
Add the chopped cabbage to the pot. It might seem like a lot, but it will cook down significantly. Stir to combine it with the onion and spices.
Pour in the chicken broth and apple cider vinegar. Stir well to make sure everything is evenly distributed.
Now add back the sausage.
Bring the mixture to a simmer, then reduce the heat to low, cover the pot, and let it cook for about 20-25 minutes, or until the cabbage is tender. Stir occasionally to prevent sticking. You want the cabbage to be soft, but not mushy.
The dish is ready when the cabbage is tender and the flavors have melded. If the cabbage needs more time, cover and continue cooking for a few more minutes.
Ladle the Cabbage and Sausage into bowls, and that is it!