neowin[.]net/news/psa-onenote-for-windows-10-is-being-killed-off-here-is-what-you-need-to-do/
There are 2 OneNotes -- one for Win10 & one in the Store. The Win10 version is getting killed off on the same day as Win10 support officially ends, Oct. 14, 2025. After that it becomes read-only. Microsoft is urging anyone using OneNote for Win10 to migrate to the Store version before then.