JorgeAmVF

autometa’s SUMUS is a simple plugin that uses the following shortcode:
<ul>
<li><code>[sumus]</code> = to reproduce the publication excerpt.</li>
</ul>
autometa’s SUMUS is a standalone component of <a href="https://wordpress.org/plugins/autometa/" rel="ugc">autometa</a> shortcodes pack.

autometa's SUMUS

It reproduces publication excerpts in pages or posts simply via: [sumus].

tepelstreel

The RSS Image Feed doesn’t create a feed of images, but ataches the first image of the post to your feeds. Normally only the content has images showing. With our plugin there will be a clickable image even in the excerpt and in the content there will be only one image instead of all the images of the post. Since version 2.2 it works as a multisite plugin as well.
The plugin was tested up to WP 4.5 It should work with versions down to 2.7 but was never tested on those.

RSS Image Feed

The RSS Image Feed adds the first image of a post to your feeds, even in firefox and even if you only display the excerpt.

autometa's SUMUS vs RSS Image Feed