The homebrew version of profanity doesn't come with plugin support. To enable it, we have to compile profanity from source. We assume you have homebrew installed.
Install the dependencies to compile profanity:
$ brew install automake autoconf autoconf-archive libtool pkg-config terminal-notifier
If you don't want notification support, omit terminal-notifier above. Now
clone the profanity repo and build it with:
$ git clone https://github.com/boothj5/profanity
$ cd profanity
$ ./bootstrap.sh
$ ./configure-plugins
$ make
If all goes well, you can run
$ ./profanity -v
which should report:
Build information:
XMPP library: libstrophe
Desktop notification support: Enabled
OTR support: Enabled
PGP support: Enabled
C plugins: Enabled
Python plugins: Enabled
GTK icons: Disabled
Then make install will install this version of profanity. If you also
installed profanity via homebrew, remember to uninstall it.