Heat oven to 350°F. Grease an 8-inch square pan.
Whisk almond flour, coconut flour, baking powder, 3/4 tsp salt, and sweetener in a bowl.
Stir eggs, almond milk, melted butter, and vinegar together. Fold into dry mix until smooth.
Spread batter in pan. Bake 18–22 minutes until golden and springy. Cool 15 minutes.
Cut cornbread into 3/4-inch cubes. Reduce oven to 300°F. Toast cubes on a sheet 12–15 minutes to dry. Cool.
Return oven to 350°F. Warm a large skillet over medium heat with butter and olive oil.
Sauté onion and celery until tender, 6–8 minutes. Stir in garlic, sage, thyme, rosemary, poultry seasoning, pepper, and 1/2 tsp salt; cook 1 minute.
Fold in the cooked sausage to heat through. Remove from heat and stir in parsley and pecans.
Combine toasted cornbread cubes with the skillet mixture in a large bowl.
Whisk warm broth with the beaten egg. Drizzle over the bowl and toss gently. Rest 5 minutes to absorb.
Transfer to a greased 9x13-inch dish. Cover with foil and bake 20 minutes. Uncover and bake 10–15 minutes until set and crisp at the edges.
Let stand 5 minutes. Garnish with extra parsley and serve warm.