2022.9 the Office 2021 installation package in Windows includes the latest official version is OneNote 2021.
One-time Purchase Classic Office 2021 from Microsoft website:https://www.microsoft.com/en-us/microsoft-365/p/office-home-student-2021/CFQ7TTC0H8N8?culture=en-us&country=US&activetab=pivot:overviewtab
Microsoft 365 includes the latest OneNote, so Microsoft 365 includes OneNote 2021.
Note: The OneNote 2019 does not exist.In 2018, OneNote was kicked out of Office 2019.
No new features will be added after the release of Office 2021 LTSC.
This type of OneNote will adds new features every month.