GTK - GTK+ is a multi-platform toolkit for creating graphical user interfaces.
Electron - Build cross platform desktop apps with web technologies
Avalonia - A multi-platform .NET UI framework
NW.js - nwjs
Qt - Powerful, flexible and easy to use, Qt will help you not only meet your tight deadline, but also reduce the maintainable code by an astonishing percentage.
NeutralinoJS - Neutralino is a lightweight application development framework.