Write is a handwriting app that works on a lot of platforms including Linux which cannot be said about most handwritten note-taking applications.

More information and demo: https://github.com/styluslabs/Write/

I’ve used it for uni on a Linux tablet/convertible and it worked really quite well and has some nice convenient features for note-taking.

The UI looks like it’s from android 4.something though ^^’

What I really appreciate about it is that its storage format are plain SVG(Z) which are extremely compatible. All you need to view your scribbles is an SVG viewer (i.e. a web browser) which basically every computer with a GUI has. Their website is in fact mostly just the output of their own app.