I’m assuming you mean a web application, however I am looking specifically for resources regarding desktop app development, I’m a pretty confident web dev, so that as an option is pretty clear to me.
qt and wxwidgets are cross platform.
You trade one set of problems (build native app) with another one (browser compatibility). There is no perfect solution when it comes to cross-platform.
Browser compat is barely an issue today. Modern web development tools and more standardization mean you just have to test your code on a few browsers, but 99% of modern JS will run the same on Chrome, Edge, Firefox and Safari.