Now that Solaris 11.4 comes with the GNOME 3.24 shell, this extension works great! It was a pain to install though as it's not a supported platform right now. Is it possible you could allow Solaris systems to install?
Unfortunately due to some reasons, this project is not longer supported. It is incompatible with recent Firefox or Thunderbird versions and there won't be any new release that will fix it.
Now that Solaris 11.4 comes with the GNOME 3.24 shell, this extension works great! It was a pain to install though as it's not a supported platform right now. Is it possible you could allow Solaris systems to install?