I suppose this depends on your point of view. QT has achieved broad acceptance as "the" cross platform solution among open source Linux-first applications, as w

I suppose this depends on your point of view. QT has achieved broad acceptance as "the" cross platform solution among open source Linux-first applications, as well as much of the open source ecosystem more generally. (Open source being what it is means that there are many exceptions, obviously.) For example, on my computer right now I have 55 applications that depend directly on qt5-base, not including libraries and parts of QT. This is also not including a ton of applications that depend indirectly on QT, including most every KDE desktop application, which depends through KDE's frameworks. So while QT may not have caught on in commercial software development, I'd say calling it a failure depends very much on what software ecosystem you're in. You might argue that HTML has achieved "universal usage" for desktop apps in a way that QT has not, but I would have to disagree. I don't have a single HTML UI or Electron app on my computer, and I don't feel as though I've given anything up. In fact I simply haven't come across any of these apps that I felt like I needed. So I might say that HTML has failed to gain mass usage on the platforms that matter to me. :-)