There are two versions of the
gpg command available in Ubuntu 16.04, in separate packages:
gnupg, which is GnuPG version 1.4.20; and
gnupg2, which is GnuPG version 2.1.11.
--locate-keys option was added in 2.0.10, as was the
nodefault value for
--auto-key-locate. Given that you're unable to use the
--locate-keys option, I strongly suspect that the version of GnuPG you're running is version 1.4.20.
To run the newer version of GnuPG on an Ubuntu 16.04 system, you need to install the
gnupg2 package, and use the
gpg2 command rather than
However, WKD support was added in GnuPG 2.1.12, which means that even using
gpg2 you won't be able to run the command given on the Tor project webpage. However...
The WKD protocol is a public one, and via the magic of tutorials like this one I've figured out that the key you need can be downloaded via HTTPS. Thus, the complete command you can use (which should, I think, work even in GnuPG 1.4.20) looks like this:
wget -O - https://openpgpkey.torproject.org/.well-known/openpgpkey/hu/kounek7zrdx745qydx6p59t9mqjpuhdf | gpg --import