I did keto consistently for 9 months last year. Wasn't cycling at the time but in my experience endurance was okay but the intensity had to remain low. That being said, when I developed a goal of completing some 70.3s I noticed my gains were slow and depressing. I began getting 90% of my carbs immediately after a workout, while remaining in ketosis, which helped a bit but my growth was still rather stunted. I abandoned keto in order to increase performance. I do 2-4 week keto stints here and there now that I am cycling and find the experience to be the same. It's doable with low intensity and my recoveries are longer and my gains smaller.