Drain and rinse the sauerkraut thoroughly to remove excess brine and reduce saltiness. Peel, core, and cut the apples into 1/2-inch wedges, and slice the onion into thin rings. Mince the garlic fresh and measure out the caraway seeds and thyme. Pat the pork loin roast dry with paper towels and season generously all over with salt and pepper, allowing the seasoning to adhere to the meat's surface. This dry surface is crucial for proper browning in the next step.

Heat 2 tablespoons of canola oil in a large skillet over medium-high heat until shimmering. Sear the seasoned pork loin on all sides for about 10 minutes total, turning occasionally, until a deep golden-brown crust forms on the outside. Once browned, remove the pork and set aside. In the same pan with the rendered fat, add the sliced onion, apple wedges, minced garlic, and fresh thyme. Sauté for about 5 minutes, stirring occasionally, until the apples soften slightly and the aromatics become fragrant.

Spread half of the drained and rinsed sauerkraut evenly across the bottom of your slow cooker. Sprinkle the caraway seeds and brown sugar over the sauerkraut and gently toss to combine. These flavors will infuse into the base layer as it cooks, creating a rich, complex foundation. Place the seared pork loin on top of the sauerkraut bed.

Arrange the sautéed apple and onion mixture from Step 2 around the pork loin in the slow cooker. Deglaze the same skillet used in Step 2 by pouring in the 1/2 cup of beer and scraping up all the browned bits from the bottom with a wooden spoon—this adds incredible depth to the sauce. Let the beer reduce slightly for 1-2 minutes, then pour this flavorful liquid over the pork and vegetables. Top with the remaining half of the rinsed sauerkraut, nestling it around and over the pork.

Cover the slow cooker and cook on low heat for 8-10 hours. The pork will become fork-tender as the gentle heat breaks down the connective tissue and allows all the flavors to meld together. During the last hour of cooking, slice the kielbasa into 1/2-inch pieces and nestle them into the sauerkraut mixture. I find that adding the kielbasa toward the end prevents it from becoming too soft and losing its texture. The kielbasa will heat through and pick up all the wonderful flavors from the braising liquid.

Once the pork is completely tender, remove it from the slow cooker and let it rest for 5-10 minutes before slicing. This resting period allows the juices to redistribute throughout the meat, keeping it moist and tender. Slice the pork into 1/2-inch thick pieces and serve atop the sauerkraut and kielbasa mixture, spooning the braising liquid and apples over everything. The dish is best served immediately while the flavors are still vibrant.