Heat the olive oil in a large skillet over medium heat. Add the potatoes, onions and peppers, then season with a pinch of salt and pepper. Cook until the onions are translucent and the potatoes begin to brown, 5 to 6 minutes.
Stir in the kielbasa and garlic. Add the beer and mustard, then stir to combine. Cover and cook until the potatoes have softened and the sausage is heated through, 2 to 3 minutes.
Remove the lid and stir in the kale. Cook until the kale has wilted, 5 to 6 minutes. Taste and adjust the seasonings as needed. Garnish with the herbs and serve straight from the skillet.