yorik

This plugin allows to place widgets on your sidebars, that fetch the contents of one or more RSS feeds, combine them by date if there is more than one, and display the thumbnail images that are included in the feeds items. You can give the widget any number of feeds, and limit the quantity of images to be displayed.
You can use any kind of RSS feed, but they must contain thumbnails (the plugin will check for, in that order, media:thumbnail tags, or enclosure tags, or, if none of these are found, an img tag inside the feed item description). If you don’t undestand a word of this, just make sure your feed carries thumbnails, otherwise all you’ll see is a “No thumbnail found” text…
You can also use this plugin from your theme templates, to display images lists anywhere else on your blog and you can easily give them a fixed size or a maximum size with CSS styling.

Image Feed Widget

A widget to display imges from RSS feeds such as twitter, flickr or youtube

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.

Image Feed Widget vs RSS Image Widget