Ubuntu – Gwibber does not respect proxy settings

This is a longstanding bug in Empathy. There is currently no fix available but perhaps others can post work arounds.

Unfortunately, you cannot.

This version of Gwibber was rewritten from the ground up, so while it has some slick features, it still misses some of its old features, which will probably return in the future if possible, but might not depending on the capabilities of the toolkit and the wishes/abilities of the developer(s).