It reads as though there's some confusion between "simplistic" with "simple". Electron is the simple answer, and "simplistic" is frequently used to try to shit on that. (Its implementation is complex. So is Qt's. But nobody cares about that for either, because it's done.) Qt's definition of "cross-platform" is functionally limited to "Windows, Mac, and Linux" unless you want to do way more work for a way worse result. That's not simple at all.

Qt runs in a web browser via WebAssembly but building an application that way--I mean, if you want that to work, good luck, but it's a presumptuous ask to make of a developer. If you want to have a client somebody can log into via Chrome or Firefox? Hi, now we have two codebases that aren't sharing logic.

Qt also doesn't work well on iOS or Android. Attempts have been made. They're not viable without significant work that "Qt is cross platform" elides, and you're probably forking your entire codebase for what you can actually salvage. And when you've built a Qt application, there's a whole lot less that's reasonably sharable when you eject out of it on those platforms (because you will), as opposed to the large amounts you can effectively share between React and React Native (see also the web-hosted option above).