Samsung starts rolling out the stable version of its One UI (Android 9.0 Pie) to the Galaxy Note 9 on the AT&T network in the US. AT&T is the first carrier in the United States to release the Android 9 Pie update for the Samsung Galaxy Note 9.
A few days ago Galaxy S9 and S9 Plus already recevied stable One UI/Android Pie update in the US.
The latest update brings January 2019 security patch for the Note 9 users. The software version is getting bumped to N960USQU1CSAA. The size of update 1.85GB. Keep in mind the size of the update is big and make sure you have enough storage.
If you own an AT&T Galaxy Note 9 and reside in the US you can check if the update is available by going into the Settings » Software update menu and tapping the Download updates manually option.