find -L . -type l
. with the directory you want to investigate, of course. Works
with both GNU and (Free)BSD find. Rationale: -L makes find act on the
(transitive closuse of the) target of a symlink -- unless the target
doesn’t exist, in which case find acts on the symlink itself. So, if the
item to act on turns out to be a symlink, it has to be dangling.