Preheat oven to 350 degrees F. Cook 1 cup rice according to package directions, using approx. 2 cups vegetable broth instead of water, adding 1 tbsp. olive oil into the cooking liquid.
Meanwhile, cut acorn squash in half and scrape out seeds. Brush 1 ½ tbsp. avocado oil onto flesh and sprinkle ¾ tsp. kosher salt and ½ tsp. pepper onto flesh. Place squash flesh-side up on baking tray and bake 45 to 60 min, until flesh can easily be pierced with a fork.
To make stuffing, preheat a large pan on medium heat. Add remaining 1 tbsp. olive oil, 8 oz. mushrooms, ½ medium red onion, and ½ tsp. each kosher salt and pepper. Stir and cook for 10 min, stirring periodically, until getting lightly browned. Add remaining ½ cup vegetable broth, 1 bell pepper, 1 tsp. Italian seasoning, and 1 tbsp. plant-based butter. Stir and cook 4 to 6 min until most of broth has bubbled away and bell pepper is tender.
Stir in remaining ingredients (juice of ½ lemon, 1 tsp. garlic powder, 1 cup chickpeas, 1/3 cup sun-dried tomatoes, ½ cup artichokes, 2 tbsp. fresh parsley), along with cooked rice.
Divide stuffing between the cooked squash, serving any extra stuffing on the side. Top with optional 1 tsp. fresh rosemary and 2 sprigs fresh thyme.