The Galaxy Note 9 and Galaxy S9 series are over two years old at this point and getting to the end of their major support lifespans. All three phones are set for one last hurrah, however, in the form of the One UI 2.5 update.
https://www.notebookcheck.net/Samsung-Galaxy-Note-9-and-S9-series-confirmed-to-receive-One-UI-2-5.489349.0.html