@electricfeet thanks for your work around saved a lot of time, it would be great to have as a tick box within the WP Featherlight Options on Pages/Posts.
In wp-featherlight\js\wpFeatherlight.pkgd.min.js, make the following changes:
1) change ".gallery-item a" to "a[data-featherlight='image']" (so that all anchors that have been picked up by Featherlight are now picked up by WP Featherlight)
2) change ".gallery, .tiled-gallery" to ".entry-content" (so that the "gallery" is now the whole of the content of the post/page).
