I saw that the Windows app beta has been released, I downloaded it and I saw that it is a webapp "hosted" by microsoft edge. I advise you to consider developing the app using Node.js and Electron.js, a fantastic library for creating webapps with HTML, CSS and Javascript. It can also be compiled for windows and all linux distributions. I hope this advice has been useful for the development of this fantastic app. It would be great having GoodNotes even on Linux!