As for a generic notes platform my favorite is crypt.ee
It's paid but they give you 100mb "free forever", which is more than enough for a whole lot of text-based notes.
Best part is it works like Google docs where there is an offline cache so you don't have to sit there and stare at it for 10 seconds waiting for it to decrypt.
They're centered in Estonia.
As for hand-written notes, I like RNote but don't really use it much, as I can't get my Wacom or Lenovo or MS pens to work on Linux. But there's nothing that comes close to OneNote in that regard.