If you go to the OneNote.com website to download the OneNote installation, by default, the download button on the website is the 32-bit OneNote installation downloader.
If you want to download 64-bit OneNote. You need to click on the "Other download options" link.
Expand Hidden Content to find the 64-bit Free Download link.
You can see the expanded hidden content:
For the best compatibility, we recommend the 32-bit version. If you already have other 64-bit Office products installed, use the 64-bit version of OneNote.
Free Download >
In hidden content, we still see that Microsoft recommends: for best compatibility, we recommend using a 32-bit version of OneNote.