Heat the oven to 350°F and arrange a rack in the middle. Cut the wheat bread in half widthwise; set one half aside. Remove the crust from the other half and discard it. Cut the bread into 1-inch cubes. Using a food processor fitted with a blade attachment, process the cubes in two batches into small, rough pieces (some will be about the size of rice kernels, others pea size), about 30 seconds per batch. You should have 3 cups of breadcrumbs. (If needed, cut more cubes from the remaining bread half and process.) Repeat with the white bread. Combine the breadcrumbs (a total of 6 cups) on a rimmed baking sheet. Spread into an even layer and bake, stirring every 5 minutes and rotating the pan halfway through the cooking time, until light golden brown and dry to the touch, about 17 minutes. Let cool, then transfer to a large bowl; set aside. (Keep the oven on.) Heat a large frying pan over medium-high heat until hot, about 2 minutes. Add the sausage and, using two forks, break it into pea-size pieces. Cook, stirring occasionally, until it’s no longer pink, about 6 minutes. Using a slotted spoon, transfer the sausage to a medium bowl. Discard any fat in the pan. Set the pan back over medium-high heat and add the butter. Once melted, add the celery, onions, and paprika. Season with salt and pepper and cook, stirring occasionally, until the onions are softened, about 6 minutes. Add the garlic and sauté until fragrant, about 30 seconds. Add the reserved sausage and the herbs and stir to combine. Add 3/4 cup of the broth and scrape the bottom of the pan with a wooden spoon to release any browned bits. Transfer the sausage mixture to the reserved bowl of breadcrumbs and stir to combine. Let sit for 10 minutes. Taste and season with additional salt and pepper as needed. If you’re using the stuffing in a turkey, let it cool to room temperature before proceeding (do not add the remaining 3/4 cup broth—the stuffing will moisten as it cooks inside the turkey). If you’re baking it separately, add just enough broth to moisten the mixture (you may not need the entire remaining 3/4 cup). Taste and season with more salt and pepper as needed. Transfer to a 2-quart baking dish, cover with a lid or foil, and bake 20 minutes. Uncover and bake until dry to the touch and golden brown on top, about 20 minutes more.