No flu / barely noticeable second time around?

So I recently started keto again, after eating SAD for a few years.

I don't really remember what it was like the first time going on keto, but this time around I barely perceived any kind of keto flu. The closest to that was being kind of foggy about 36 hours in, but not experiencing headaches or nausea or anything like that. I'm happy not to experience the flu, lol, just concerned that maybe it meant I didn't actually enter ketosis?