As they are closed source no one can tell you their true privacy policy. It seems better than average from what I’ve read but you never know…
Personally I use logseq and sync the files via a Nextcloud instance. I can only recommend it, although I also recommend spending an hour to learn the tagging and linking logic and reading through their guide on what’s possible. I still only leverage a minor part of the potential myself.
One that is closer to onenote (I think, never used onenote) is Joplin.
You have several long and comprehensive answers so please allow me to add an emotional one:
Fucking compile error in hour six of what you estimated to be a four hour compile job because of a mistake you made that you found within 5 seconds after the error!!
Fucking why doesn’t this compilation start I can’t find my mistake for hours?!
Where does this module come from?! What do you mean “root kit”? Learning was fun!
It all was fun! :)