It's already in qt5.14

src/htmlexport.cpp

@@ -30,11 +30,7 @@ static QString cleanChars(const QString &txt);
 namespace {
 auto returnEndLine()
 {
-#if (QT_VERSION < QT_VERSION_CHECK(5, 15, 0))
-    return endl;
-#else
     return Qt::endl;
-#endif
 }
 }
 //@cond PRIVATE