The release of the new Samsung Galaxy S9 and S9+ have been the talk of the town recently. Although the phones are just incremental updates, the recent news regarding the smartphones have been centered around the new variable aperture and the re-positioned fingerprint scanner. They are also the first Samsung devices to get the Android Oreo 8.0 update meaning they are now compatible with Project Treble. This means these devices will have an easier time compared to previous Samsung phones in getting AOSP Android Oreo running.
Someone testing this out was able to get a Project Treble Generic System Image (GSI) running on an Exynos Galaxy S9, which will hopefully pave the way for future development on the new devices.
Not too long after the launch of the S9/S9+ the kernel source code for the phones were released getting the developer community started on work for the device right away. Only a couple of weeks later Team Win Recovery Project (TWRP) released an official build for both devices.
A custom recovery such as TWRP is necessary in order to install a custom ROM with ease because it allows you to create a full backup of your device so if anything goes wrong you can just wipe and restore your device to how it was before the failed custom ROM install.
An XDA Senior Member iamnotkurtcobain tested out AOSP Android Oreo 8.0 on his Exynos Galaxy S9 thanks to help from XDA developer minz1. The ROM he tested was phh-Treble ROM by developer phhusson and according to his usage most of the main features worked fine. Currently the Android Oreo 8.1 update does not work so the developers had to use the older 8.0 system image which is why the security patch seems older.
Keep in mind this currently only works on the Exynos Galaxy S9/S9+, because the bootloader needs to be unlocked on the device which it is for the Exynos variants. Unfortunately the Snapdragon variants do not come with an unlocked bootloader, so for all the US Galaxy S9/S9+ owners you may be waiting a while for an unlock for your bootloader.
This is still exciting news for S9/S9+ owners as it shows there is a lot of progress to be made in the development regarding the Galaxy S9/S9+.