You can use any sort of pork meat when making this traditional polish sauerkraut soup. Given you’re making it in the slow cooker, it can be raw or cooked. So it’s a great option for leftover pulled pork or ham.
If you aren’t able to find fermented sauerkraut or even the canned, glass jar version…which is the second best…and need to get the tin-can sauerkraut…make sure and rinse it a couple times before using it in your recipe.