Samsung no longer plans to offer software upgrades for the Galaxy Note 9 since the device has been decommissioned. The list of phones that are now supported indicates that: It now includes the Galaxy Z Flip4 and Galaxy Z Fold4; however, Note 9 is not included.
Among all the smartphone manufacturers, Samsung is among the top regarding software support. Note 9 came pre-installed with Android 8.1 Oreo when it was introduced in 2018. Later, he got Android 9 in 2019 and Android 10 in 2020
The model kept getting security upgrades every three months after that, but now the frequency of updates has been altered. Instead of receiving monthly security patches, they will now get quarterly updates.
Remember that Android 9 was already preloaded on the Galaxy Note 10 and Galaxy Note 10+ when they were announced in August 2019?