In Qt 5.15.0 Beta 4 a WebAssembly app with the Virtal Keyboard does not load because of:

qtloader.js:382 QQmlApplicationEngine failed to load component
qtloader.js:382 qrc:/main.qml:23:5: Type InputPanel unavailable
qtloader.js:382 qrc:/QtQuick/VirtualKeyboard/content/InputPanel.qml:32:1: module "QtQml" is not installed

It works if the app is built for Windows.
It worked with Qt 5.14.0 Beta 2(emsdk 1.39.0).

I also found a workaround for the problem, add to main.qml Line 1:

import QtQml 2.14

I attached the project to reproduce and the built wasm apps.