Samsung is now rolling out a new software update to the unlocked Galaxy S8/S8+ and Galaxy Note 8 in the US. The latest software update adds the November 2018 security patch, few bug fixes, and minor improvements.
The build number is N950U1UEU5CRK1 for the Galaxy Note 8, and the size is 62 MB. The build version is G950U1UEU5CRK3 and G955U1UEU5CRK3 for the Galaxy S8 and S8+ respectively. The size is 105 MB.
If you want to check this update manually, head into Settings > Software update > Download updates manually or you can simply wait till the update automatically appears in your phone.