The three are receiving new updates in Europe, where the Note 9 update is arriving as software version N960FXXS2ARH6 while the S9 and S9+ are on versions G960FXXS2BRI1 and G965FXXS2BRI1, respectively.
These are OTA updates and usually, such updates take time to arrive on all units. This means that some users may get the download notification ahead of others, so don’t fret if your friend’s S9 or Note 9 has already received the September patch and yours hasn’t.
Related: Samsung Android 9 Pie update news
To speed up things, you can try forcing the update via the Settings menu of your phone, but there’s no guarantee this will yield the expected results.