T-Mobile and AT&T owned Galaxy Note 9 units are already updated to Android Pie version. Now the Samsung has expanded this android pie roll out for two more US variants - Verizon and Unlocked. This software update has been officially confirmed through the Samsung official forum and Verizon support page. The update brings new software version PPR1.180610.11.N960USQU1CSB3 for Verizon and N960U1SQUEU1CSB3 for Unlocked. The OTA size for unlocked version will be in 1671.64 MB (1.67 GB), while the Verizon didn’t specify the size.
The pie update for Galaxy Note 9 brings all new Samsung One UI with refreshed design, adaptive battery & brightness, gesture navigation, app actions, one-handed mode, dark theme mode, revamped camera UI, video beauty, WiFi calling, performance tweaks and other bug fixes. Samsung will push this major software update in usual OTA method, so use recommended internet connection like WiFi for uninterrupted download.
The OTA roll out will come in batchwise, so it will take some time or even days to reach all devices. You can also check for the update from Settings menu to know whether the firmware is available for your device or not.