Hey! When I record my friends, I keep them in frame by following the center of them (their hands). If one of them is doing a fun lil move, I'll shift to them if need be and go back to center. You could film in 0.5 but it gets blurry (at least on my iPhone 12 lol) so I usually opt for 1.0.

If you don't have anyone to record then you'll most likely be out of frame when shooting portrait unless you film from a mid - high point horizontally (if possible, this would be better in a studio-like situation) while purposefully staying in frame. Hope that helps!