It works once you figure out how to fine-tune it

Works well, though a bit finicky and lacking in simple features. The “class” filter doesn’t work well if you are using the block editor (as the CSS class you add to an image via Gutenberg system will assign the class not to the image, but to the entire image block, which will give you broken-image errors by targeting that class). You are better off using the CSS Selectors filter include the ‘img’ tag (eg: .lightbox1 img) so it picks up the correct element when clicking. Ultimately the plugin could consider a simple checkbox somewhere in the interface to enable the Lightbox on an image, eliminating the more complex CSS filters for people who may not have this kind of knowledge. Would also be great to instead have a way to eliminate certain classes (include everything by default, except…) rather than the opt-in method, which can be cumbersome when retrofitting a website with this plugin.

Once you have it working though, it certainly does what it says on the tin. It just took me way too long to figure out about the quirky class vs. class selector system, I feel there are definitely methods to make this more clear or easier to use.