Samsung has slowly been rolling Android Oreo out to supported Galaxy devices for the past few months - it has been available in beta form since November - but the majority of unlocked versions in particular are still left waiting.
Samsung has said this is because unlocked versions of the Galaxy smartphones need to go through more rigorous testing to ensure they work with whatever mobile network you choose to use. Carrier-locked versions on the contrary are only made to handle one network, so don't require as much testing and so are eligible for updates sooner.
The good news is that Samsung says all eligible devices will soon get the latest version of Android, although can't yet give exact dates. We will update this piece as and when we know more, but in the meantime, keep checking for a software update in settings of your Galaxy device.
Samsung devices on Android Oreo 8.0 will get the the Samsung Experience 9.0 software, which is the company's own skin that runs over the top of Android. Updates include being able to manage notifications for supported individual apps in the Quick Panel, the position of the Edge panel can be changed by pressing and holding on it and higher-quality Bluetooth audio codecs including AAC and Sony's LDAC gain support.