Currently Oreo is in Beta which was available to s8 and s8+ owners who registered to be Beta Programme Testers.
Last time I checked Samsung had sent out the 2nd update so far.
Until the Beta Programme Testing has reached its final stage and then released it wont be available.
Daily Driver > Samsung Galaxy s²⁴ Ultra 512Gb ~ Titanium Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help. " This is the way. "