Morgan Kay

If you use a service such as Feedburner or MailChimp to turn your RSS feed into an email subscription, and the images in your posts are more than 600px wide, the formatting of your HTML emails might be messed up. This plugin lets you resize the images in your RSS feeds.
Version 2.0 has been completely re-written from scratch! It is now more reliable, and works with images from external URLs.

RSS Image Resize

Resize images in RSS feeds so they will fit in HTML emails.

zackdesign

RSS Image Widget fetches images from any RSS/Atom feed that uses enclosures and displays them in a responsive grid with a built-in lightbox. Works as both a classic widget and a Gutenberg block.
Features:
<ul>
<li>Widget + Block — Use in sidebars (classic widget) or anywhere in the block editor</li>
<li>Lightweight — No jQuery, no external CDN. Just a tiny vanilla JS lightbox (~2 KB)</li>
<li>Responsive grid — CSS Grid layout adapts to any container width</li>
<li>Lazy loading — Images use native browser lazy loading</li>
<li>Accessible — Lightbox supports keyboard navigation (Escape to close)</li>
<li>Zero configuration — Just add a feed URL and go</li>
</ul>
Upgrading from v2.x:
The Bootstrap classes (<code>row</code>, <code>col-xs-12</code>) and external Lightbox2 CDN have been replaced with clean semantic HTML, a responsive CSS Grid layout, and a bundled vanilla JS lightbox. If you had custom CSS targeting the old classes, you will need to update it to use the new <code>.rss-image-gallery</code> BEM classes.

RSS Image Widget

Display images from an RSS or Atom feed as a widget or block with a lightweight lightbox gallery.

RSS Image Resize vs RSS Image Widget