Flavor does not matter, presentation does not matter but the food shouldn’t make you sick, and should ideally have enough calories per day for the average person to survive (2000 kcal min).
Edit: I am not in any danger of starving or malnutrition, nor am I insolvent. I’m mainly asking this question out of curiosity on how people would approach a solution :)
Not necessarily just rice. The thing is that both beans and cereals contain protein, but each has only some of the essential amino acids, while human body consumes these acids in a particular proportion. Well whaddayaknow, beans and cereals in combination have all of those acids, complementing each other. So wheat or other cereals also work instead of rice.
They even have about 10% protein, which is on par with sausages and such.