I've known about the so-called immediate-mode UI (
https://github.com/ocornut/imgui) for some time, which uses OpenGL to create interfaces. They were initially designed for Games but some people insist on using them for desktop apps.
The most interesting thing is that someone managed to replace the OpenGL part with Fenster (
https://github.com/zserge/fenster a 2d canvas directly in xlibs) and the result was, to say the least, something unique so far. A fusion of IMUI and Canvas. The result is a rich, beautiful desktop application with absolutely no dependencies beyond xlibs.
https://bernsteinbear.com/blog/fenster-microui/