Answer: Lima beans are far too starchy to be compatible with keto eating.
Each serving of lima beans (1 cup) contains 23.2 g of net carbs. Sadly, that's far too carb-heavy to fit the keto diet.
As a rule of thumb, beans do not fit the keto diet. They tend to be high in starches and low in fat, the opposite of what you want on keto.
If you need a bean to satisfy your bean craving, black soy beans are a popular keto-friendly bean. They're high in protein, rich in antioxidants, and only contain 2 g of net carbs per cup.