In addition to the official September security patch from Google and the usual bug fixes and minor tweaks, the latest firmware update for the Samsung Galaxy Note 9 also comes with noticeable camera improvements, including day/night HDR control accuracy enhancements, better low light brightness, and more.
https://www.notebookcheck.net/Samsung-Galaxy-Note-9-gets-an-update-with-camera-improvements-and-the-latest-security-patch.336384.0.html
I have downloaded this latest update since 3 days ago but I haven't realised any significant picture quality enhancements.