Keto doesn't fit well with cycling IMO, the necessity for carbs if one is going to ride hard and long is just too great. And apparently any carbs consumed for keto is really bad. Though if one is only basing their performance on their own past performances, then it's probably doable.
A Mediterranean or almost vegetarian or even a pure vegetarian diet works well and isn't affected by carbohydrate use while cycling. And the new craze I think... flexitarian. Which is someone that is mostly plant based but might eat any meat every now and then will also work well.