Preheat the oven to 350°F (175°C).
In a medium saucepan, bring the chicken broth to a boil. Add the rice, reduce heat to low, cover, and simmer for 18-20 minutes until rice is tender and liquid is absorbed. Remove from heat and fluff with a fork.
While the rice cooks, melt 2 tablespoons of butter in a large skillet over medium heat. Add the chopped onion and minced garlic and sauté for 3-4 minutes until softened.
In a large mixing bowl, combine the cooked rice, sautéed onion and garlic, shredded chicken, drained pineapple chunks, chopped green and red bell peppers, shredded cheddar cheese, sour cream, mayonnaise, milk, salt, black pepper, dried thyme, and paprika. Mix well to combine all ingredients evenly.
Transfer the mixture into a greased 9×13 inch casserole dish and spread evenly.
In a small bowl, mix the crushed cornflakes with melted butter. Sprinkle this mixture evenly over the top of the casserole.
Bake in the preheated oven for 35-40 minutes until the casserole is bubbly and the topping is golden brown.
Remove from the oven and let it rest for 5 minutes before serving.