class Foobar : public QObject {
    Q_OBJECT
    QML_ELEMENT
    QML_UNCREATABLE("Read only")
    Q_DISABLE_COPY(Foobar)

public:
    Foobar(QObject* parent = nullptr) : QObject(parent) {}
    Q_INVOKABLE int baz() const { return 42; }
};

class Druggeljug : public QObject {
    Q_OBJECT
    QML_ELEMENT
    QML_SINGLETON

public:
    Druggeljug(QObject* parent = nullptr) : QObject(parent) {
        for (int i = 0; i < 5; ++i) {
            m_foos.append(new Foobar(this));
        }
    }

    Q_INVOKABLE QList<Foobar*> getList() const { return m_foos; }

private:
    QList<Foobar*> m_foos;
};

function showList() {
        const l = Druggeljug.getList()
        for (const foo of l) {
            console.log(foo.baz())
        }
    }

Warning: main.qml:12:30: Could not compile function showList: return type QList<Foobar*> cannot be resolved [compiler]
        const l = Druggeljug.getList()
                             ^^^^^^^