[ubuntu] Cant get any sound due to lack of support of my audio chain, any help / solutions?

Welcome. Have you tried a hunt for 'ubuntu firewire' or 'ubuntu thunderbolt' or 'ubuntu <name-of-your-outboard-device-here>'? Might shed some light. And both of them together looks even more promising.

Screwed? Probably not. I have no experience with using Thunderbolt but sure there are others that do. I do have experience with Firewire and know that works fine. In the meantime, could you provide a couple more bits of pertinent info, please.

Name of outboard audio device
Release and flavour of Ubuntu (Ubuntu Studio 14.04 for example)

Perhaps start with testing the chain. With nothing plugged in to the thunderbolt/firewire port does Ubuntu see the thunderbolt card is there? If so, move on. Plug in the device and open a terminal and run this immediately:

dmesg

Also if not, and you know Ubuntu is seeing the thunderbolt card and firewire, post the output of that last bit of the dmesg between code tags, please (see link in my signature for code tags).

PS: Also, what is making you suspect it is not working now? You mention '... then I plug my device in' then you can't get any sound. What are you doing to find it? Do you suspect Ubuntu is not seeing the Thunderbolt card or the adapter? How are you detecting that Ubuntu is not recognising the Firewire device? Because you can't see it?

You might try tweaking Pulseaudio Volume Control. Not sure if that's installed in Ubuntu by default but it is in the repos (Ubuntu Software or Gnome? Not certain what's being used now).