runtime error: module is not installed when using qt_add_qml_module()

[timjquetee]

I'm following various examples and documentation trying to learn how to use qt_add_qml_module() to create a simple module mymodule using cmake and have my windows QML application import and use that module.

I get the following error message at run-time:

qrc:/main.qml:4:1: module "modules.mymodule" is not installed

I think I am missing some fundamental understanding or step.
The file modules/mymodule/CMakeLists.txt is:

cmake_minimum_required(VERSION 3.16)
qt_add_qml_module(mymodule
    URI modules.mymodule
    VERSION 1.0
    QML_FILES MyRect.qml
    SHARED)

The file modules/mymodule/MyRect.qml is:

import QtQuick
import QtQuick.Controls.Basic
import QtQuick.Layouts

Item {
    id: root
    implicitWidth: 50
    implicitHeight: 50
    Rectangle {
        color: "blue"
        anchors.fill: parent
    }
}

The main.qml file imports this module and tries to display a MyRect:

import QtQuick
import modules.mymodule

ApplicationWindow {
    id: root
    visible: true

    width: 1000
    height: 800

    MyRect {

    }
   ...

The CMakeLists.txt for the main application includes the following:

qt_add_executable(mytestapp main.cpp)
set_target_properties(mytestapp PROPERTIES WIN32_EXECUTABLE ON)
target_link_libraries(mytestapp PRIVATE Qt6::Core Qt6::Gui Qt6::Qml Qt6::Quick)
qt_add_qml_module(mytestapp URI main VERSION 1.0 QML_FILES main.qml NO_RESOURCE_TARGET_PATH NO_PLUGIN IMPORTS modules.mymodules)

find_program(WINDEPLOYQT_EXE windeployqt.exe)
add_custom_command(
    TARGET mytestapp POST_BUILD
    COMMAND ${WINDEPLOYQT_EXE} --no-translations $<TARGET_FILE:mytestapp > --qmldir ${CMAKE_CURRENT_SOURCE_DIR}
    COMMENT "Running windeployqt for target mytestapp "
)

And the main.cpp is:

int main(int argc, char **argv)
{
    QGuiApplication app(argc, argv);
    app.setApplicationName(QFileInfo(app.applicationFilePath()).baseName());
    QQmlApplicationEngine engine;
    engine.load(QUrl("qrc:/main.qml"));
    return app.exec(); 
}

I have been able to work-around the error if I change mymodule to be built as a STATIC library instead of SHARED, and also explicitly add mymodule to the target_link_libraries() of the main applicaiton. I don't understand why using STATIC works, but using SHARED doesn't. When using a SHARED library for mymodule, I can see the .dll file mymodule.dll being copied to the application build directory, but the error says "module "modules.mymodule" is not installed". What does 'installed' mean in this context?