Heat the oil in a large sauté pan over medium heat. Add the onions and sauté until translucent, about 10 minutes. Add the potatoes and sauté, stirring every few minutes, until they’re tender, another 15 to 18 minutes.
Add the paprika, smoked paprika, salt, and pepper. Sauté until the spices are fragrant, about 1 minute. Add the kale and sauté until it’s just wilted but still vibrantly green, 2 to 3 minutes. Remove the pan from the heat and transfer the potato mixture to a large serving bowl.
Take the kraut out of the jar with a clean fork, letting any extra brine drain back into it. Roughly chop the kraut and add it to the potatoes, tossing thoroughly to incorporate.
Serve immediately, while the potatoes are still warm.
Note: Try soaking cubed potatoes in a bowl of water for an hour to help release the starches, which will help prevent sticking. Drain and lightly dry the potatoes with a towel before cooking.