Just for the record.
If you have these two in the mailcap:
text/html; lynx %s; nametemplate=%s.html
text/html; lynx -nonumbers -dump %s; copiousoutput; nametemplate=%s.html
The first entry still works in the "view-attachments" i.e "v" command in the main
pager, but mutt has changed in the way, that if you use "Enter" on the attachment,
the line with "copiousoutput" is used. And if you use "m" i.e force mailcap use,
the first line is used, and you see the page in the real lynx window.