With the “Do not save external image locally” setting, the external image is just an image link.
There is no lightbox.
It looks a little old …
UX is not good for forums with lots of external images
For forums where images are posted more often, you should uncheck the “download remote images to local” setting to disable it.
However, with the current UX, image links are just image links, so I get the impression that they are old and difficult to use.
Some people complained on my forum.