Lynx  currently has no support for @longdesc.
@longdesc provides "link to long description (complements alt)".
See: http://www.w3.org/TR/html4/index/attributes.html
Example: <img alt="Chart fo the development" longdesc="description-of-chart" src=i.jpg >
Example page:http://malform.no/testing/longdesc/img@longdesc.html

Any chance that Lynx, with its history as a accessibility web browsers, could implement @longdesc support?

I have a concrete proposal for how it should be implemented The best approach seems to me to be to implement it as if the image is an image map, where the URL inside @longdesc represents the link of the image map.

Thus, practically speaking, I would expect @longdesc to work just like the following image map example - which is an example that has been crafted solely in order to show one may mimic the @longdesc behavior by using a simple image map: [1]

|1] http://malform.no/testing/longdesc/ARIA+area@rel=longdesc.html

One particular detail: For image maps, the link text is provided via the @alt attribute of the <area> element. However, for @longdesc, screenreaders such as the well known Jaws, offers a "hard coded" link text. In Jaws's case, the hard coded text is "Press enter for long description". And hence the page on the link above (http://malform.no/testing/longdesc/ARIA+area@rel=longdesc.html) provides the "Press entor for long description"  as the link text for the image map replication of the @longdesc.

Whether Lynx should do the same, or if Lynx should simply present the address of the link as link text, or have a hard coded text, is probably up for debate. Or a combination: Offer a hard coded short text, in combinatio with the URL. Something like this:

Long description: http://example.com/long/desc.html

The latter seems optimal to me.

PS: I have also filed the same bug for Elinks ... text browsers have pretty uniform support for image maps, and I hope that they could implement @longdesc uniformly too: http://bugzilla.elinks.cz/show_bug.cgi?id=1104