Potatoes, Greens and cheese. you can live on this for years and not suffer significant health problems. You may get bored but you will not starve. Beans rice and greens, same idea.
Also to lump 'potatoes' as one item is madness. there are so many varieties each with it's own taste, texture and nutrient profile.
Blue, orange, yellow, rose. round, lumpy, fingerling, oblong. mealy waxy, fluffy, creamy, buttery. Baked, fried, boiled, roasted. they're all good.