I ate only keto for years and I'm getting back to it now so I have some experience to speak of.

You are correct, fruit is mostly sugar so no fruits. Some keto adherents allow the occasional handful of berries, but I found that just made me unreasonably hungry later on. Not everyone has this reaction, though.

There is plenty of fiber in above-ground vegetables. And even if there wasn't, it's not like eating only meat would kill you, humans evolved on the plains and/or jungles of Africa where meat was almost all that was easily available.