On a fresh install of Fedora, I tried installing Jitsi but was getting a horrible error. Didn't matter which SIP account I used or how I had my audio set up, I consistently got this error:

net.java.sip.communicator.service.protocol.OperationFailedException: An error occurred while sending invite request
[...]
Caused by: net.java.sip.communicator.service.protocol.OperationFailedException: An error occurred while creating session description
[...]
Caused by: javax.sdp.SdpException: The parameter is null

Only by running Jitsi from the command line was I able to find the actual source of the issue.

java.net.UnknownHostException: phineas: phineas: Name or service not known

My computer is named "phineas" and apparently Fedora doesn't automatically add that name to the /etc/hosts file on install. That was pretty easy to resolve.

$ cat /etc/hosts
127.0.0.1 localhost.localdomain localhost
::1 localhost6.localdomain6 localhost6
127.0.0.1 phineas

Of course, you don't have to name your computer phineas too.