Section 5.7.1 in x11-wm.html in the Handbook says to install Gnome, use 'pkg install gnome2'. That doesn't work, but 'pkg install gnome3' does.
A commit references this bug: Author: bjk Date: Sat Apr 23 20:46:04 UTC 2016 New revision: 48719 URL: https://svnweb.freebsd.org/changeset/doc/48719 Log: Change gnome2 references in the handbook to gnome3 gnome2 isn't there anymore. PR: 209001 Submitted by: Paul Hoffman Changes: head/en_US.ISO8859-1/books/handbook/x11/chapter.xml
Changed to gnome3 (also the ports installation part a couple paragraphs later) in r48719. Thanks for the report.