If You Can't Wait for Samsung...
If you can't wait for the official Samsung Galaxy S7 Oreo release, you can install a pre-release version of Android 8.0 on your device right now.
Developers have released a pre-release version of the Samsung Galaxy S7 Android 8.0 Oreo update with Samsung Experience 9.0 features on board including Bixby.
Unfortunately, the update is for the Snapdragon version of the Samsung Galaxy S7 and not the Exynos models.
Manually updating to Android Oreo can take time and cause problems, but if you're feeling impatient, the option is there.
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