Update: One UI 2.5 OTA update is now rolling out for Galaxy S9 and S9+ in Germany, Europe with build number G960FXXUCFTJ2, and G965FXXUCFTJ2 respectively for the Exynos variants. The OTA will soon come to Asia and North American region with Snapdragon variants. It comes with the latest October 2020 security patch level.
Original: Samsung is currently beta testing Android 11 update with One UI 3.0 firmware. While the manufacturer did promise 3 years of Android OS upgrades to their flagship phones, this does not include the Galaxy S9 series and the Note 9 series. It is only limited to the 10th gen devices like Galaxy S10 series and above. However, Samsung did promise One UI 2.5 firmware upgrade for the Galaxy S9 and Note 9. It is now rolling out with the latest build number FTJ1.
The Galaxy S10 and Note 10 series have already received One UI 2.5 firmware update for both – Exynos and Snapdragon variants (United States). Here is One UI 2.5 OTA update for Note 9 with build number N960FXXU6FTJ1. The OTA is currently live in Germany, Europe for the Exynos Note 9 (SM-N960F) variant. It will soon come to other regions including Asia and North America. The OTA also features October 2020 security patch level.
The reason why you should be most excited about One UI 2.5 is because it brings most of the Note 20 (Ultra) features to the Galaxy S-lineup. The Note 20 series launched with this firmware. While the update is still based on Android 10, it features Wireless DeX, enhanced Pro video mode, the ability to change Single Take duration and, much more. The complete changelog is listed here. While we may not see all the Note 20 features come to Note 9 and S9 series, this is the last major firmware upgrade for the devcies. So this is your best bet.
The Snapdragon variants of the Galaxy S9 series and the Note 9 series will also receive One UI 2.5 based on Android 10, but that would take some time. So we can expect it later this month or the next month. This is due to various carrier restrictions from T-Mobile, Sprint, Verizon, and much more in the United States.
You can download the full stock firmware for Samsung Galaxy S9, S9+, and Note 9 from our tutorial here.