Gamevase

In the default Gutenberg gallery, whenever you click a gallery image, you either navigate to another page and see the linked image or you cannot click and see a bigger version of the image at all.
This plugin shows Gutenberg gallery images in a lightbox on the same page.

Simple Gallery Lightbox

Adds a simple lightbox to default Gutenberg gallery.

Martin von Berg

Provides an easy was to add a Lightbox to Images in Gutenberg image, gallery and Media-with-Text-Blocks. Additionally to Youtube and HTML5 Videos but no other videos. Other video types like VideoPress, Vimeo etc. are currently NOT supported. 
The Javascript library fslightbox.js is used for that. You even may use the paid version of fslightbox.js. 
Plugin settings are provided by a JSON-file that may be easily changed and backed-up manually (automatically after V2.0.0).
NEW: Added support for the complete HTML-code to the post, page etc. in-between body tags and not only the content. This is an Opt-in. See example settings file in ./settings/plugin-settings-body.json.
The support for HTML5-Videos and Youtube-Videos will add a small red button on the top left of the embedded Youtube-Video which opens the lightbox with that video. 
YT-Videos could be disabled by deleting the line <code>"wp-block-embed-youtube"</code> in the file <code>plugin-settings.json</code>. If you do so please delete the comma at the end of the line before, too! 
See live example here: https://www.berg-reise-foto.de/software-wordpress-lightroom-plugins/wordpress-plugins-fotos-und-karten/
The support for Youtube-Videos is working with the given functionality and extended to stop running videos onOpen and for the paid version to stop running videos on slideChange.
<h3>Plugin uses</h3>
Following libraries and WP-Plugins were used to create this plugin:
<ol>
<li><a href="https://fslightbox.com/" title="fslightbox.js" rel="nofollow ugc">fslightbox.js</a></li>
<li><a href="https://github.com/ivopetkov/html5-dom-document-php" title="HTML5DOMDocument by ivopetkov" rel="nofollow ugc">HTML5DOMDocument by ivopetkov</a></li>
<li><a href="https://wordpress.org/plugins/kodefix-lightbox-gallery/" title="Lightbox Gallery by Kodefix" rel="ugc">Lightbox Gallery by Kodefix</a></li>
</ol>

Simple Lightbox for WordPress

Provides an easy was to add a Lightbox to Images in Gutenberg image, gallery and Media-with-Text-Blocks. Additionally to Youtube and HTML5 Videos but  …

Simple Gallery Lightbox vs Simple Lightbox for WordPress