Chop the shallot and lemon into quarters (reserving some lemon for later garnish). Smash the garlic.
In a slow cooker or instant pot set on high/simmer, pour in the stock. Add in the shallot, lemon, garlic, black pepper, Parmesan rind, a handful of parsley, and bay leaves. Cook on high for at least 4 hours.
Prepare the pasta according to the package directions, draining 2 minutes shy of the recommended time. Toss with 2 tablespoons of olive oil and set aside.
20 minutes before the stock is ready, make the meatballs. Form the sausage into 1/2 ounce balls (about a centimeter wide). In a wide sauté pan set over medium heat with 2 tablespoons of the olive oil, brown the sausage on all sides, 7-8 minutes.
Finish the soup: strain out the soup into a large bowl or other appropriate vessel. Discard the stock solids and return the broth back to a simmer. Once simmering, add in the greens and sausage and simmer for 4-5 minutes along with a pinch of salt. Once the greens are wilted, the soup is ready. Serve in a wide bowl with a bit of pasta on the bottom, topped with a squeeze of lemon and a sprinkle of Parmesan. Enjoy!