Right, but QT apps are QT apps -- they're not really native on any platform which is the same problem you run into with Flutter an Electron.
If you want an app that has platform semantics on every major platform then you need separate code bases. If you want an app that has the same semantics on every platform then you go with a cross-platform toolkit.
So you are arguing that no one "would say re-writing the same app 5 times and maintaining 5 codebases is a bad idea."?
That was my statement. You are saying it's not true. All the upvotes suggest some would say that. Therefore my statement is true.
I'm not sure why you're so confused here. This isn't at all applicable to what you are saying. You are talking about writing an app once and having one code base, which is exactly the opposite of what I was talking about. You have constructed a straw man and called it not true.
I'm working with C++/Qt/QML/Javascript. No need to maintain 5 codebases.
Just a single codebase compiles to at least 9 platforms: Linux, Windows, macOS, iOS, Android, *BSD, Raspberry, QNX and WebAssembly.