Samsung Galaxy S9 and Samsung Galaxy S9 + smartphones will no longer receive software updates. The early 2018 flagships are now off Samsung’s lists of devices eligible for security updates.
The Galaxy S10 series meanwhile were moved from monthly to quarterly updates, now that they are over 3 years old.
The Galaxy S9 series is following the path of its predecessors. Back in early 2021, Samsung demoted the S9 from monthly to quarterly security updates, when the Galaxy S8 was completely taken off the list, and the same thing happened to the Galaxy S7 phones a year earlier.
The Galaxy S9 series’ last major update was to One UI 2.5 package, received in late 2020.