For those of you who want to upgrade to Android 8.0 Oreo on your Samsung Galaxy S8 or S8 Plus early, here’s how to do it easily. Root is NOT required for the upgrade and also this is a 100% stock firmware so you won’t lose Samsung Pay if you are not rooted. Also, this method DOES NOT ERASE DATA since it is a stock firmware. But we do highly recommend you to make a backup just in case things go wrong. For rooted users, this method WILL REMOVE ROOT. You will have to re-root and that requires erasing data so if you absolutely need root, wait for the TWRP flashable version instead of this method.
First, make sure you have a supported model and download the upgrade:
Also grab ODIN & Drivers – Link