Building and installing what exactly ?

@TenG
Be aware that not all of Qt modules are supported in WASM. Before anything, check the list at https://doc.qt.io/qt-5/wasm.html#supported-qt-modules against what is in your app. For example, it doesn't do databases, you can't access the local file system, and so on. Also I noticed this time that it requires a Qt static build, but maybe you have to have that for iOS anyway, I don't know.

If it works for you it's a really simple solution compared to rewriting anything. Just check out the gotchas.

This topic came up a couple of weeks ago in this thread: https://forum.qt.io/topic/58097/browser-ui (and see also the older https://forum.qt.io/topic/45217/qt-qml-on-standard-web-browser ); no ideal solutions to automagically-webify-my-existing-Qt-app though unfortunately (although QmlWeb looked like it had a lot of potential).