Thanks for reaching to us here wondering why your well-loved Samsung Galaxy S9+ doesn't receive an updates since a year ago.
Your Samsung Galaxy S9 + was released in March 2018 with Android 8.0 (Oreo) OS and is upgradable to Android 10, One UI 2.5.
And Samsung has committed that select devices launched in 2019 or later will be supported with firmware security updates for a minimum of four (4) years following their global launch.
Monthly, quarterly, and biannual firmware security updates will include patches for Android OS-related security issues released by Google as well as patches for Samsung-specific security issues.
For more assistance and guidance, you may contact us via our online Samsung Customer Care support channels below.