I am able to connect to gTalk, in Pidgin or Empathy. In Empathy, I have connected my SIP account and can call landline phones through it.
However, when I right-click on any of my gTalk contacts in Empathy, video call and audio call are grayed out.
I have the gstreamer bad and ugly plugins, I have the libav codecs, and ffmpeg. The Empathy FAQ explicitly lists gstreamer0.10-ffmpeg as a required package, but I think the FAQ must be outdated because this package isn't available anymore for Ubuntu (I'm on 18.04).
In any case, if I can make an audio call with SIP, I should have the codecs to make an audio call over gTalk. It's also grayed out in Pidgin, if I open a chat with a contact and browse to media in the menu. Audio Call, Video Call, and Audio / Video Call are all grayed out.
