The Samsung Galaxy S8 and Samsung Galaxy Note 8 have a new “Samsung Experience” UI and, of course, the Bixby assistant. A user over on the Samsung Community asked about getting that new UI and Bixby on his Samsung Galaxy S7. An admin has this to say:
Thanks for part of Samsung community. Would like to tell you bixby is supported in Galaxy S8 & S8+ and N8. We plan to support more models gradually in the future.
Also would like to tell you new UI interface can be available with the next update so please wait till the update comes in your device.
There’s no technical reason that Bixby can’t run on older devices. They won’t have a dedicated button to launch it, but the app should still work. So it’s nice to hear they will be supporting more phones. The new UI is coming in the next update, which probably means Oreo. If you don’t feel like waiting for these features, you can get them yourself.