"QtWebEngine is not installed" warning even though it is - urgent

[franco.amato]

I am developing an application using QML and I need to use WebEngineView to render some webpages.
I need to build it in both Windows and Linux (Ubuntu)

In my top-level cmake I fing the package in this way:

set(QT_COMPONENTS Widgets
    WebEngineQuick
    Qml
    Quick
    Svg
    Gui
    Network
    NetworkAuth
    LinguistTools
    PrintSupport
    Core5Compat
)

find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS ${QT_COMPONENTS})
find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS ${QT_COMPONENTS})
....
target_link_libraries(${PROJECT_NAME} PRIVATE
     ....
    Qt6::Qml
    Qt6::Quick
    Qt6::WebEngineQuick
   ...
)

Then in the Main.qml I import and use it

import QtWebEngine
.... more code ....
    WebEngineView {
        id: webView

        anchors {
            top: topContainer.bottom
            left: leftToolbar.right
            bottom: bottomBorder.top
            right: rightBorder.left
        }
        settings.localContentCanAccessRemoteUrls: true

        Component.onCompleted: {
            console.log("URL:", url)
        }

        onCertificateError: function(error) {
            error.defer()

            // Display information about the error
            console.log("Certificate error: " + error.description)
            console.log("Error type: " + error.type)
            console.log("URL: " + error.url)

            if (error.overridable) {
                error.acceptCertificate()
            }
        }
    }

I have no problems in building it for Windows and in Linux (Debug mode) but I get this warning

[warning] qrc:/Qml/Main.qml:5:1: module "QtWebEngine" is not installed (qrc:/Qml/Main.qml:5)

when trying to build under Linux in Release mode. I installed the QtWebEngine module using the Maintenance tool. I am using Qt 6.8.1. I can also see the lib in the Qt installation lib folder

So I don't understand why in debug mode it detects it and in release mode it's not.
Any help please

[franco.amato]

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