HTTP/2 request does not finish until closed by remote host

#include <QCoreApplication>
#include <QNetworkAccessManager>
#include <QNetworkReply>

int main(int argc, char *argv[])
{
  QCoreApplication a(argc, argv);

  //QUrl url("https://www.google.com/");  // this works
  QUrl url("https://api.dataforsyningen.dk/orto_foraar_DAF?SERVICE=WMS&REQUEST=GetCapabilities");  // does not work
  QNetworkAccessManager manager;
  QNetworkRequest request(url);
  request.setAttribute(QNetworkRequest::Http2AllowedAttribute, true);  // works fine if http2 is not allowed
  QNetworkReply *reply(manager.get(request));
  QObject::connect(reply, &QNetworkReply::downloadProgress, [reply](qint64 received, qint64 total) {
      qDebug() << "download progress " << received << total;
    });
  QObject::connect(reply, &QNetworkReply::finished, &a, &QCoreApplication::quit);
  a.exec();
  qDebug() << "done. " << reply->error() << " / " << reply->errorString();
  return 0;
}