When the Galaxy S8 was initially released, it lacked support for Google's Daydream VR platform. But at Google I/O, the company confirmed that the phone would receive an update "over the summer" that added Daydream support. Then T-Mobile said the update was coming, followed by Verizon.
Now it looks like it's finally happening. The Google VR G+ account announced that "the Daydream-ready update is rolling out now" to both the S8 and S8+. It seems like this is a server-side switch, rather than a system OTA update. One user on Reddit said that clearing the Google VR Service app's data enabled Daydream support.
Let us know in the comments if Daydream is working on your Galaxy S8. You can grab the main app from the widget below.