Please click the following link to download ns-3.32, released October 7, 2020:

For users of the ns-3.31 release, a patch is available to update code to ns-3.32, at this link. Other patches to migrate older versions of ns-3 (back to ns-3.17) to subsequent release versions can be found in the same directory; they must be applied sequentially to upgrade across multiple releases.

The sha1sum of the ns-allinone-3.32.tar.bz2 release archive is ce9c09e2b7b93cf12fa61b7fdbb12c49d2302e8c.