ButtonGroup {
     buttons: column.children
 }

 Column {
     id: column

     RadioButton {
         checked: true
         text: qsTr("DAB")
     }

     RadioButton {
         text: qsTr("FM")
     }

     RadioButton {
         text: qsTr("AM")
     }
 }

Warning: main.qml:13:19: Cannot assign binding of type QQmlListProperty<QObject> to QList<QObject *>
         buttons: column.children
                  ^^^^^^^^^^^^^^^
Error: main.qml:13:34: Could not compile binding for buttons: cannot convert from QQmlListProperty<QObject> of QQuickItem::children with type QQuickItem to QList<QObject *> of QList<QObject *>
         buttons: column.children
                                 ^