Okay, ich habe es geschafft.
init() {
const modalDataAttr = Feature.isActive('V6_5_0_0') ? 'data-bs-toggle="modal"' : 'data-toggle="modal"';
const modalPlugin = window.PluginManager.getPluginInstanceFromElement(document.querySelector(`[${modalDataAttr}][data-url]`), 'AjaxModal');
modalPlugin.$emitter.subscribe('ajaxModalOpen', this.onModalOpen.bind(this));
}
onModalOpen(event) {
// your code here
}