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.
The most important features when handwriting IMHO are selection tools and then being able to manipulate the selected strokes.
Write implements a multitude of selection tools such as lasso which most tools have but much more useful to me were ruled selection which selects based on lines on a ruled paper and path selection which selects every stroke you touch with your selection stroke.
You can then move the selected strokes in a ruled manner, so for example I’d select a whole line of strokes and move them down a few lines. This is incredibly useful and brings many of the freedoms we enjoy in editing text on a computer to handwriting.
Re-flowing using stroke divisors is an amazing feature in theory but I’ve never been able to make it work reliably enough for my purposes, so I personally disabled that particular feature.
The undo/redo dial is also pretty neat.
Once you actually try to take real notes or solve some mathematical problems, you’ll really come to appreciate such features and will dread using any note taking application supposedly made for handwritten notes that does not implement such features.