Please click the following link to download ns-3.35, released October 1, 2021:

For users of the ns-3.34 release, a patch is available to update code to ns-3.35, 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-3.35.tar.bz2 release archive is 943a19c6b92b36d923671ae90a065f7ffb0dbabc