Blog/_layouts/feed.xml

<?xml version="1.0" encoding="utf-8"?>
{% if page.xsl %}
  <?xml-stylesheet type="text/xml" href="{{ '/feed.xslt.xml' | absolute_url }}"?>
{% endif %}
<feed xmlns="http://www.w3.org/2005/Atom" {% if site.lang %}xml:lang="{{ site.lang }}"{% endif %}>
  <generator uri="https://jekyllrb.com/" version="{{ jekyll.version }}">Jekyll</generator>
  <link href="{{ page.url | absolute_url }}" rel="self" type="application/atom+xml" />
  <link href="{{ '/' | absolute_url }}" rel="alternate" type="text/html" {% if site.lang %}hreflang="{{ site.lang }}" {% endif %}/>
  <updated>{{ site.time | date_to_xmlschema }}</updated>
  <id>{{ page.url | absolute_url | xml_escape }}</id>

  {% assign title = site.title | default: site.name %}
  {% if page.collection != "posts" %}
    {% assign collection = page.collection | capitalize %}
    {% assign title = title | append: " | " | append: collection %}
  {% endif %}
  {% if page.category %}
    {% assign category = page.category | capitalize %}
    {% assign title = title | append: " | " | append: category %}
  {% endif %}

  {% if title %}
    <title type="html">{{ title | smartify | xml_escape }}</title>
  {% endif %}

  {% if site.description %}
    <subtitle>{{ site.description | xml_escape }}</subtitle>
  {% endif %}

  {% if site.author %}
    <author>
        <name>{{ site.author.name | default: site.author | xml_escape }}</name>
      {% if site.author.email %}
        <email>{{ site.author.email | xml_escape }}</email>
      {% endif %}
      {% if site.author.uri %}
        <uri>{{ site.author.uri | xml_escape }}</uri>
      {% endif %}
    </author>
  {% endif %}
  
  {% if page.tags %}
    {% assign posts = site.tags[page.tags] %}
  {% else %}
    {% assign posts = site[page.collection] %}
  {% endif %}
  {% if page.category %}
    {% assign posts = posts | where: "categories", page.category %}
  {% endif %}
  {% unless site.show_drafts %}
    {% assign posts = posts | where_exp: "post", "post.draft != true" %}
  {% endunless %}
  {% assign posts = posts | where_exp: "post", "post.hidden != true" %}
  {% assign posts = posts | sort: "date" | reverse %}
  {% for post in posts %}
    <entry{% if post.lang %}{{" "}}xml:lang="{{ post.lang }}"{% endif %}>
      {% assign post_title = post.title | smartify | strip_html | normalize_whitespace | xml_escape %}

      <title type="html">{{ post_title }}</title>
      <link href="{{ post.url | absolute_url }}" rel="alternate" type="text/html" title="{{ post_title }}" />
      <published>{{ post.date | date_to_xmlschema }}</published>
      <updated>{{ post.last_modified_at | default: post.date | date_to_xmlschema }}</updated>
      <id>{{ post.id | absolute_url | xml_escape }}</id>
      {% assign excerpt_only = post.feed.excerpt_only | default: site.feed.excerpt_only %}
      {% unless excerpt_only %}
        <content type="html" xml:base="{{ post.url | absolute_url | xml_escape }}"><![CDATA[{{ post.content | strip }}]]></content>
      {% endunless %}

      {% assign post_author = post.author | default: post.authors[0] | default: site.author %}
      {% assign post_author = site.data.authors[post_author] | default: post_author %}
      {% assign post_author_email = post_author.email | default: nil %}
      {% assign post_author_uri = post_author.uri | default: nil %}
      {% assign post_author_name = post_author.name | default: post_author %}

      <author>
          <name>{{ post_author_name | default: "" | xml_escape }}</name>
        {% if post_author_email %}
          <email>{{ post_author_email | xml_escape }}</email>
        {% endif %}
        {% if post_author_uri %}
          <uri>{{ post_author_uri | xml_escape }}</uri>
        {% endif %}
      </author>

      {% if post.category %}
        <category term="{{ post.category | xml_escape }}" />
      {% elsif post.categories %}
        {% for category in post.categories %}
          <category term="{{ category | xml_escape }}" />
        {% endfor %}
      {% endif %}

      {% for tag in post.tags %}
        <category term="{{ tag | xml_escape }}" />
      {% endfor %}

      {% assign post_summary = post.description | default: post.excerpt %}
      {% if post_summary and post_summary != empty %}
        <summary type="html"><![CDATA[{{ post_summary | strip_html | normalize_whitespace }}]]></summary>
      {% endif %}

      {% assign post_image = post.image.path | default: post.image %}
      {% if post_image %}
        {% unless post_image contains "://" %}
          {% assign post_image = post_image | absolute_url %}
        {% endunless %}
        <media:thumbnail xmlns:media="http://search.yahoo.com/mrss/" url="{{ post_image | xml_escape }}" />
        <media:content medium="image" url="{{ post_image | xml_escape }}" xmlns:media="http://search.yahoo.com/mrss/" />
      {% endif %}
    </entry>
  {% endfor %}
</feed>