Bring brown rice, quinoa, amaranth, millet, wheat bran, salt, and 6 cups water to a boil in a medium pot. Reduce heat, partially cover, and simmer, stirring occasionally, until cereal is the consistency of porridge (softer and thicker than the usual bowl of oatmeal) and water is absorbed, 40–50 minutes. Do ahead: Porridge can be made 5 days ahead. Let cool; cover and chill. Assembly Heat coconut oil in a medium skillet over medium-high. Cook coconut flakes, stirring often, until toasted, 2 minutes; transfer to a plate. Add apple, cinnamon, and 2 tablespoons honey to skillet and cook, stirring occasionally, until apples are browned in spots and tender, about 3 minutes. Serve porridge topped with apples, coconut, sea salt, bee pollen, and a drizzle of honey, if you like.