Preheat the oven to 400ºF. Line a baking sheet with parchment paper.
Add the cornbread cubes to the baking sheet and spread them into an even layer. Bake for 10 minutes. Toss and roast for another 10 minutes or until the croutons are golden brown. Remove the croutons from the oven and reduce the oven temperature to 375ºF.
Meanwhile, heat the olive oil in a large skillet set over medium/high heat. When the olive oil is fragrant, add the onion and shallot and cook for 2 minutes. Add the garlic, carrots, celery, and 1/8 teaspoon of salt and sauté for an additional 3-4 minutes.
Add the Brussels sprouts, thyme, and sage to the pan and cook for 2 more minutes. Remove the pan from the heat and set aside.
In a medium bowl, whisk the eggs, vegetable broth, garlic powder, remaining salt, and maple syrup together. Set aside.
Grease a 9x13-inch casserole dish. Add the cornbread croutons, wild rice, and vegetable mixture to the prepared dish. Mix well right in the dish.
Pour the egg mixture over the cornbread/rice/vegetable mixture and use a spatula to combine everything. Make sure the croutons are really soaked in the egg mixture.
Drizzle the melted butter over the top of the cornbread stuffing and bake for 50 minutes (at 375ºF). If you notice the stuffing is browning too quickly, tent a piece of aluminum foil over the top of the casserole dish halfway through baking.