Although feijoada is often crowned with the title "Brazil's National Dish" it is not, in fact, a dish at all. Feijoada is a meal, in the same sense that Thanksgiving turkey dinner is not a dish but a meal. Just as one family might serve creamed pearl onions at Thanksgiving, while another family considers that heresy, and serves a broccoli casserole instead, the core ingredients of the Thanksgiving dinner rarely vary - turkey, stuffing, mashed potatoes, gravy, etc. Feijoada is exactly the same - there are a huge number of dishes that have made their way into a feijoada, but there is only a small number of dishes without which one cannot really call the meal a feijoada.
A true feijoada will consist, at the very least of:
Cuts of pork, including hocks, ears, and belly, cooked in black beans
Linguiça sausage cooked in black beans
Peeled slices or cuts of fresh oranges
Together, all these dishes constitute a proper feijoada, but other additional dishes may be added as desired. Note that the first two ingredients, the true core of a feijoada, are pork products cooked in black beans. Although in today's world, with today's sensibilities, vegetarian feijoadas do exist, the traditionalist Brazilian would refuse to call that concoction a feijoada at all. But if the 21st century universal compendium of food has allowed the entry of vegetarian haggis or a vegetarian pasty, then let's allow an exception for vegetarians to allow them to enjoy feijoada. However, truth be told, a true feijoada is a meal for carnivores only.