Personally I'm a user of QOwnNotes and I have it sync up with my Nextcloud install. It takes a bit to get set up, you can move all the panels around and basically create your own layout, but it's the closest I've gotten to a good note-taking application along the lines of Onenote.
There are a bunch of simpler options like Gnote, Simplenote, "Notes", etc. that may be worth taking a look at as well.
Alternatively you can use OneNote Web.