I have intalled Jitsi desktop 2.11.5610 on two new computers OS = MINT 19 Mate
On both of them, I have the same problem : when making a call, the receiving party hears ringing, but after answering, there is no sound. The only remedy is to go to Options and change the input setting from defaut to the device (or vice-versa, it does not matter, as long as you “touch” the input setting, you can even change it and then revert it to what it was), then it works. The problem, is that you have to do that for each call.
EDIT: I have now intalled new release 2.11.5611 on both computers : it is worse than ever, as what was the “remedy” with the previous version is now leading to a sound freeze or sometimes to a general freeze.