This is with a new install of Ubuntu Studio 22.04
It has always been a challenge to get Firewire multichannel interfaces working in Linux using qjackctl, and this was the first time of trying with the new install. I plugged it in and started the computer. The interface started up and connected without using qjackctl. It appeared as an option in the list of system audio-out ports.
All attempts to run qjackctl failed. I ran Reaper (a DAW) and saw all of the input and output ports appear as I am used to, almost. I played a track and the sound appeared in the headphone ports 5&6. And 7&8. And 1&2. I needed to disable remixing by changing a line in ~/.conf/pulse/daemon.conf to,
remixing-use-all-sink-channels = no
I needed to stop pulse repeatedly trying to add the Saffire as a system audio output and input port because it was continually failing to set up the system audio. All attempts to kill autospawn, and pulseaudio, itself (yes, I tried that as well!) failed.
Ubuntu Studio was connecting the Saffire as a system Stereo In and Stereo Out interface. Anything routed to Ports 1&2 came out of the Line Out socket. I tried Studio Controls and disabled the pulse bridge and removed the Saffire options from the system Mic and Output options, but no change in Reaper. I configged Studio Controls to use FFADO with no change. I found a way to start the jack daemon in terminal and use the qjackctl features. All the correct auto-Connections were made, but I could only get an output on ports 1&2 and this came via the headphone port on Outputs 5&6.
Then I noticed that the port designations in the Reaper Routing were scrambled. In earlier versions of US and in Windows, the inputs appeared as eight mono ports: Saffire Pro Line 1&2 1, Saffire Pro Line 1&2 2. Saffire Pro Line 3&4 1, Saffire Pro Line 3&4 2... HD Audio Line Input 1, HD Audio Line Input 2 and then presented as stereo ports: Saffire Pro Line 1&2 1 (Stereo M/C), Saffire Pro Line 1&2 2 (Stereo M/C) Pro Line 3&4 1 (Stereo M/C)... HD Audio Line (Stereo).
I think that these are derived from the output of ffado-test Discover.
With the current version of US, they looked superficially the same, but there was a sequence of eight firewire_pcm00130e0100060f3e_L, followed by two firewire_pcm00130e0100060f3e_S, followed by eight firewire_pcm00130e0100060f3e_L (Stereo M/C) and then one firewire_pcm00130e0100060f3e_S (Stereo M/C).
It was a similar situation for the output ports. I'm assuming that Reaper is trying to make sense of the system allocating a stereo pair for output and input to an audio interface that it knows has 10 inputs and 10 outputs, but that is just a guess.
It seems that even with selecting the FFADO driver rather than alsa, removing the pulse bridge ports from Studio Controls and getting the Saffire out of the system volume port list, alsa is not presenting the 10 x 10 port interface correctly.
From my surfing, it seems that jack runs with the ports enumerated by alsa, but why this latest version of Ubuntu Studio is making such a pig's ear of it, I don't know.
I tried a Focusrite Scarlet 16 x 16 USB interface and the situation is better. I can route the sound to the headphone ports rather than ports 1&2. However, the designations in Reaper are scrambled and port 5&6 seems to be connected to the DAW sockets for 8&9. Again, there were the correct number of input and output ports. The various qjackctl panels (Graph, Connexions and Patchbay) showed all the correct sockets, connections and patches, but something interferes between qjackctl and the DAW.
I tried with Ubuntu Studio 22.04 Live with exactly the same results. Out of the box, Ubuntu Studio seems fine for a firewire or USB external stereo audio interface, but cannot cope with multichannel, no matter what I tweak.