You are posting in self hosted by also referencing some software that isn’t so I’m not sure exactly what you’re asking for in that regard.
Saber is the only non-onenote notes software that supports handwriting and is fully FOSS, to my knowledge. I use that and then back up with Syncthing.
Gotcha. I like Saber for handwritten notes. It also supports photos and PDFs, so I will get some meeting notes, upload them into Saber and then handwrite notes on top of the PDFs.
It is cross-platform and has native NextCloud support, and they’ll even give you a server to use if you sponsor the project.