It's been discussed quite a bit in this forum (or the S8 one) so you can search for more info. But there is no way to actually change the lock screen time in settings. However, some have had success finding a theme that did alter the clock. I just don't recall which themes were successful.
As a workaround, I just have the samsung weather app provide me consistent updates and it appears as a constant notification item that I don't dismiss. When you have any notification, the lock screen clock will appear the way you want (with the minutes beside the hour).
Also, I think I read that in the Oreo beta, there was a way to change the lockscreen clock. Not absolutely certain if my memory is correct.