The Beyond Burger only contains 3g of carbs, making it perfectly acceptable for a Ketogenic diet, as far as I understand it. The Impossible burger contains more, at 9g, but that's easy to fit into most carb allowences of Keto (not many go for <10g/day).

Even with a goal of 0g of carbs per day there's a lot of room on the plate for above-ground vegetables and natural oils.

Beef is an okay food, but there's lots of alternatives that seem to outperform it for many metrics.