I use this OpenBoard fork with Swype-like typing: https://github.com/erkserkserks/openboard/releases

I believe it is exactly what you want.

And it looks like this:

https://forum-dangerousthings-com.s3.us-west-002.backblazeb2.com/original/3X/7/f/7f19394211783aee8d88a7b0ec4e6f80c87e8940.mp4

and in other languages:

https://forum-dangerousthings-com.s3.us-west-002.backblazeb2.com/original/3X/b/2/b22f24f7bd8ef581bf76977ec279f0148563ea6f.mp4

AFAIK no open source library exists. Open implementations of gesture typing do exist (FlorisBoard had it some time ago, though it's going through a significant rewrite still) but the lib loading on OpenBoard is specially intended to use Google's proprietary libraries. (Which is why it's an external download and not built-in)

Or that's what the state of things were the last time I checked.

Thanx its working, not just for English but other languages also. Does anyone know how to automatically save words that don't show up when writing text or that contain my proofreading? Thank you for your help.