I use OneNote on KDE Neon in a Windows 10 virtualbox. Yes, it's not the most efficient but I have found this approach much faster than using the sluggish web UI for OneNote. I also use my Windows 10 virtualbox for the rest of the MS Office suite through a university subscription, so I feel it justifies the 30GB of disk space it takes.

There is OneNote online, it's a little slimmed down from the desktop app though.

I use the online versions of OneNote and also the other Office 365 apps (Word, etc.) on Linux laptops. Great to have.