Select Galaxy Note 9 models, namely the international variants with the Exynos 9810 processor, have started receiving the December 2020 security patch. Germany was the first country to receive the update for these smartphones. The new update has build number N960FXXS6FTK3 and does not contain any additional changes.
As usual, it will take some time for the update to reach all regions. To check if the update is already available on your smartphone, open the Settings menu, find and select the "Software Update" section, then click on "Download and Install". Most likely, the Galaxy Note 9 models with Qualcomm's Snapdragon 845 will start receiving the December 2020 security update within a week.