I installed Android 12 on Samsung S9 #Worlds1st working on S8 - YouTube
This is Noble rom, an android 12 custom rom for the Galaxy Note 9 and S9 by AlexisXDA on XDA. It has some bugs but nothing that's deal breaker, some stuff have
Install Android 12 on Galaxy S9 and S9 Plus (LineageOS 19.1) - How to Guide! - YouTube
Android 12 also arrives on Samsung Galaxy S9/S9+ and Note 9 with this ROM - Real Mi Central
Android 12 (One UI 4) now available for Samsung Galaxy S9 and Note 9 using Noble ROM 2.0 - RPRNA
Install Android 12 on Galaxy S9 [How To]
Samsung Galaxy S9,S9 Plus One Ui 4.0 Android 12 Update [ Confirm Date ] Samsung S9,S9Plus New Update - YouTube