05 January 2021
UPDATE (January 28th, 2020):
A new SamMobile report has revealed that Samsung has begun rolling Galaxy S9 Android 10 update. The stable build is available for both Galaxy S9 and Galaxy S9 Plus flagships. One important thing to keep in mind is that the update is arriving on devices that are running Android Pie. It means if you are One UI 2.0 beta tester, you will have to wait for some time.
It is an over the air update and you should receive an update notification anytime soon. In the meantime, one can also check for the update manually by visiting Settings -> Software Update section.
Original (November 27th, 2019)
As promised last week, Samsung has released the Galaxy S9 and Galaxy S9 Plus Android 10 beta update. It is being rolled out in the form of One UI 2.0, the latest iteration of Samsung's custom Android skin. It is reported to be available for download for beta testers in India and South Korea.
The process of enrolling in the beta program as it has been for the Galaxy Note 9, Galaxy Note 10, and Galaxy S10 devices. You will need to install the Samsung Members app on your device. It will show you a banner confirming that the beta program is live. Tapping on the same will take you through the registration process. If selected, you will receive an update notification with the latest beta build.
One can also check for the update manually by visiting the device's system settings. The update size is said to be 1.8 or 1.9 GB depending on the device you have. It is advised to connect to a WiFi network before downloading the update as it is heavy in size. Since it is a beta build, you can also backup your data before installation. It will help you in unwanted situations that may happen during the process.
As mentioned in the beginning, it is an Android 10 beta build which means you will get all the new Android 10 features. It includes a system-wide dark mode that will work with all the apps that are compatible. There are a number of One UI related features and improvements as well.