It depends. Training with low insulin levels can increase breakdown of protein to make glucose, but if you are already 10+ hours into a fasting window, that also raises growth hormone levels and the ketones can replace the need for muscle derived glucose (protein->glucose). Growth hormone does not rise as much if you eat a calorie restricted diet but don’t restrict the time period, or don’t train in a fasted window.
You did not mention being in a calorie restricted diet or trying to lose bodyfat at all which should be the first thing to mention for advice on this if it is the case, since it will dictate whether you need peri-workout nutrition to meet your goals, so I begin with the assumption from your post that you are not restricting calories, but simply eating a ketogenic diet, and training for performance and muscle gain without gaining fat. On a ketogenic diet, your muscles don’t even use glucose very well since they get loaded with fatty acids, and they stop making glucose burning enzymes. If anything, carbs around a workout on a ketogenic diet cat shut of ketones and reduce fat mobilization and decrease your available energy, and growth hormone (which also can improve performance).
Putting carbs around training in a calorie deficit with balanced macros makes sense. It makes no sense if you are keto adapted, which is different, by the way, from simply having some ketones in your blood (0.2-0.8 or so).