Preheat oven to 375°F (190°C).
Cook sausage in a large skillet over medium heat until browned.
Remove sausage and set aside, leaving drippings in the pan.
Melt butter in the same skillet and sauté onion and celery until soft.
Add diced apple and cook for 2–3 minutes.
Transfer sausage, vegetables, and apples to a large mixing bowl.
Add bread cubes, sage, thyme, salt, and black pepper.
Pour in warm chicken broth and mix gently until moistened.
Transfer mixture to a greased baking dish.
Bake uncovered for 35–40 minutes until golden on top.