Samsung is pushing a new software update for the Galaxy S9+ users. The Galaxy S9 Plus is getting an April 2019 Security patch update, bug fixes, and performance improvements on T-Mobile, Sprint and Unlocked variant in the US.
A new update is available for the S9 Plus for users of Sprint and T-Mobile as version G965USQU4CSC8. While the Unlocked Galaxy S9 Plus getting this update on Version G965USQS4CSC8. The size of the update 526MB.
If you are still waiting, you can download the newest update build by going into Settings > Software updates and tapping on “Download updates manually”.