Preheat the oven to 300°F and set a rack in the middle.
Add the bacon to a large Dutch oven (or any heavy, oven-safe pot with a tight lid) and turn the heat to medium. Cook, stirring often, until the bacon renders it fat and turns crisp, about 5 minutes. Use a slotted spoon to remove the bacon to drain on paper towels. Remove most of the fat, leaving about 2 tablespoons in the pot.
Add the sausages in a single layer, being careful not to crowd the pot. Work in batches, if necessary. Cook, turning occasionally, until golden brown all over (sausage won’t be fully cooked at this stage), about 7 minutes. Remove sausages to a plate and set aside. Repeat with remaining sausages, if necessary.
Add the onions, along with a pinch of kosher salt (the bacon and sausages are both salty) and black pepper, and cook, stirring occasionally, until onions turn soft and slightly golden, about 7 to 10 minutes. If the bottom of the pot threatens to burn, add a tablespoon or so of water and scrape the bottom of the pot with the spoon.
Add the garlic and tomato paste and cook, stirring often, for 1 minute. Reduce the heat to low, whisk in the flour and cook for another minute, whisking constantly. Stir in the beer, stock, Worcestershire sauce, bay leaves and thyme and bring to a simmer.
Add the potatoes and bacon to the pot. Cut the sausages in half on a steep angle and add them as well. The liquid won’t cover the sausages and that’s fine. Cover the pot with the lid, and bake in the oven for 1 1/2 hours. Remove the pot and stir in the kale. Return the pot to the oven and bake, uncovered, for 15 minutes longer. Taste and adjust the seasoning as needed.