Samsung’s 2018 flagships, the Galaxy S9, S9+, and Note9 are currently receiving a software update that adds a dedicated Night Mode to their cameras.
The Galaxy S10 shipped with an automatic Night Mode that worked only whenever the camera felt it was needed. And users found that annoying. It wasn’t long before Samsung released an update to add it as a separate mode that can be manually activated by the user.
That same feature is what is now rolling out to Samsung Galaxy S9, S9+, and Note9 cameras.
If you are impatient, you can always do a manual check to see if the update ready for your device. Dive into your phone Settings and go to Software update -> Download and install.