If you do not use multiple "scrset" settings for the thumbnail image this code will work. Basically it changes the base64 conversion of the "src" that is done on export to all images back to the "src" link that was used inside the program.
<script>
function init() {
var imgDefer = document.getElementsByTagName('img');
for (var i=0; i<imgDefer.length; i++) {
if(imgDefer[i].getAttribute('srcset')) {
imgDefer[i].setAttribute('src',imgDefer[i].getAttribute('srcset'));
} } }
window.onload = init;
</script>
(Put this in your footer)
Again, this script will only work if you do not choose to have different image sizes or resolutions at different breakpoints for you image. (thumbnail link in your case)
I would love for someone to take this one step further and make the script work for multiple "scrset" settings.
It would also be great if CC would allow us to choose if the image should be converted or not as I understand the reasoning of a fast loading web site but SEO indexing of images is just as important to some of us.
I suppose one could argue though if this script works you may get the fast loading of the base64 image and also the SEO indexing of the non-converted image.jpg link that replaces it.
I have a link to a working fancybox
http://gluexp.coffeecup.com/fancybox.html with a small thumbnail gallery with only the one "srcset".....and then a gallery below it that uses two different sized images at different breakpoints.....that does not work (thumbnails missing) because of the multiple srcsets involved. I have not yet figured out a way to script a fix for that.
Bootstrap 5 CSS Grid.