may work:
<script>
function layoutRequest(hypeDocument, element, event) {
if (window.matchMedia("(orientation : portrait) and (device-width : 414px) and (device-height : 896px) and (-webkit-device-pixel-ratio : 3)").matches) {
hypeDocument.showLayoutNamed('Your_iPhone_XS_max_layout')
}
}
if("HYPE_eventListeners" in window === false) {
window.HYPE_eventListeners = Array();
}
window.HYPE_eventListeners.push({"type":"HypeLayoutRequest", "callback":layoutRequest});
</script>