I've heard Pavel say there are many successful techniques. What has worked before still works. Pick a style and stick with it if it works for you. (paraphrasing)
Depending on how much extension you get in your neck, some might say not to do it for long term resilience, but that was true when the advice was first given.
I just looked at the SFL course manual, and they recommend looking at a spot on the floor 6-10 feet away, or as high as the horizon/straight ahead. It makes no mention of looking up at the ceiling, but says there should be mild neck extension and not hyperextension.
The "many successful techniques" have to do with each individual lifter's strengths and weaknesses on any lift. E.g., my posterior chain is strong - my back is stronger than my legs. In order to break a heavy deadlift off the floor and get it high enough for my posterior chain to really kick in, I have to maintain a neutral neck and, at times in my lifting career, I have looked straight down in order to fire what needs help to make my lift
In Beyond Bodybuilding it’s mentioned looking down off the floor, to use more quads, and look up past the knees, to use more posterior. It’s an advanced technique, but interesting.
I prefer a packed neck for most lifts. Think “make a double chin”. If your interested in neck packing I am sure Google would be helpful.
There's a video on the SF YouTube channel where Pavel talks about this: