.add interprets strings as HTML in the same way as .append, .prepend, .before, .after, .replaceWith, so no-append-html should scrutinize it in the same way.
const untrusted_input = "<img src=x onerror=alert(1)>";
const $oops = $().add(untrusted_input); // should trigger no-append-html, but doesn’t
$("<body>").append($oops); // XSS
.addinterprets strings as HTML in the same way as.append,.prepend,.before,.after,.replaceWith, sono-append-htmlshould scrutinize it in the same way.