IFTTT cannot take subheadings from RSS, coded in XML 0.1

Question

The web app » IF THIS THEN THAT « doesn't seem to have an "ingredient" for the text right below the headline. Here is the code of the existing ATOM (RSS) Feed:

<?xml version="1.0" encoding="UTF-8"?>
<feed xml:lang="de-DE" xmlns="http://www.w3.org/2005/Atom">
  <id>tag:DOMAIN,2005:/artikel</id>
  <link rel="alternate" type="text/html" href="WEBSITE"/>
  <link rel="self" type="application/atom+xml" href="FEED URL *.atom"/>
  <title>WEBSITE's NAME</title>
  <updated>2019-04-11T06:00:00+00:00</updated>
  <logo>BANNER.png</logo>
  <icon>FAVICON.ico</icon>
  <entry>
    <id>tag:DOMAIN,2005:Article/ID-NUMBER</id>
    <published>2019-04-11T10:00:00+00:00</published>
    <updated>2019-04-11T12:00:00+00:00</updated>
    <link rel="alternate" type="text/html" href="EntryURL"/>
    <title>ARTICLE's TITLE</title>
    <summary type="xhtml">
      <div xmlns="http://www.w3.org/1999/xhtml">
<p>SUB-HEADLINE.</p>
      </div>
    </summary>
    <content type="xhtml">
      <div xmlns="http://www.w3.org/1999/xhtml">
<p><img src="SYMBOLIC HEADER IMAGE.jpg" alt="ARTICLE's TITLE"/></p><p>EntryCONTENT</p>
      </div>
    </content>
  ...