Preheat the oven to 375 degrees F. Melt 6 tablespoons butter in a large pot or Dutch oven over medium-high heat. Add the sausage and cook, breaking it up with a wooden spoon, until lightly browned and no longer pink, about 6 minutes.
Add the celery, onion and bell pepper; season with 1 teaspoon salt and a few grinds of pepper and cook, stirring occasionally, until softened, about 6 minutes. Add the kale and 1/2 teaspoon salt and cook, stirring, until just wilted, about 1 minute. Add the chicken broth and bring to a simmer, then remove from the heat and let cool slightly.
Whisk the eggs and cilantro in a large bowl. Add the cornbread, potato bread and broth mixture and gently mix until all the bread is moistened.
Butter a 3-quart baking dish. Add the stuffing and dot with the remaining 2 tablespoons butter. Cover with foil and bake 30 minutes. Uncover and continue to bake until golden brown, 20 to 30 more minutes.