Building and running a CMake based application with Qt 6.4.0 for WebAssembly (from installer) using emsdk-3.1.6 works fine.
But doing the same with qmake-based applications does fail when launching the application. That concerns basically all Qt examples that are still qmake based.
The error is:
Application exit (SyntaxError: Document.querySelector: '!qtcanvas_13439344' is not a valid selector)