We do recommend dairy free for at least the first 2-4 weeks. Helps get weight moving. Most things there are pretty easy dairy free subs (coconut milk for cream, coconut oil for butter). But cheese and cream cheese are tougher subs. We have a coconut milk based cream cheese recipe coming in our next cookbook (you can also google for one that doesn’t add sugar).
Diary free is trickier, but definitely can be done (our Keto-30 Advanced meal plan package is 100% dairy free 30 days of meal plans).