In the month of August, the Galaxy Note 9 flagship will be three years old but Samsung is still providing new software updates every month. A few days ago, this device had received the latest Android patch in Germany, and the company is now pushing the same firmware to the US unlocked units.
At the same time, this OTA improves the Quick Share tool for enhanced file sharing between Galaxy devices. However, the Galaxy Note 9 had already lost its eligibility to get any major s/w update, which means it will spend its remaining time on the One UI version 2.5 on top of the Android 10 operating system.
Like every time, Samsung is releasing the new Galaxy Note 9 June 2021 security patch update in a staged manner, so it may take a while to be available for every US unlocked unit. Till then, you can check for the update manually by navigating to your device Settings >> Software updates >> Download and install.