In Totalmix do the routing from software playback channels 1/2 to the hardware output channels 9/10
'Flash current mixer state'
Use this feature of Totalmix to save the routing into the device.
otherwise you have to force all app developers changing their app for using channels 9/10 instead of 1/2.
Most apps are fix using channels 1/2 no matter what the system channels are set to.

Different apps like browser etc. all use playback channles 1/2, all is mixed together and recorded at once.
There is no way to separate the audio as these apps has no option to select different audio outputs.

No, about software in general.
Audio-multichannel compatibility is usually not available in free software.
Media players, internet-browsers, video conference tools, etc.

But the internet browser not.
And Pipewire can't divide the different sources of audio when those come ahead on the same channel.
Beside the browser what are those different sound sources ?

The desire is unclear, I was referring to post 3 where audio recording contains video background from browser...

I'm running CachyOS (k6.17.4-4-cachyos).
Found a wireplumber solution that works for me so i'm adding it here for future reference.

In a terminal run: wpctl status

• This should produce a list of Pipewire clients, audio and video devices.

• Find your device and remember the number infront of it.

• In my case i have a Digiface USB and it had the number "54".

Next run the following command: wpctl inspect {ID} | grep "device.bus-id"

• Replace {ID} with the number of your device

• Copy or note down the bus-id of the device

Now create a configuration for wireplumber. In my case i created a file in:

/etc/wireplumber/wireplumber.conf.d/10-map-stereo-channels.conf

with the following content:

monitor.alsa.rules = [
  {
    matches = [
      {
        node.name = "~alsa_output.{YOUR-BUS-ID}.*"
      }
    ]
    actions = {
      update-props = {
        audio.position = "AUX0,AUX1,AUX2,AUX3,AUX4,AUX5,AUX6,AUX7,AUX8,AUX9,AUX10,AUX11,AUX12,AUX13,AUX14,AUX15,AUX16,AUX17,AUX18,AUX19,AUX20,AUX21,AUX22,AUX23,AUX24,AUX25,AUX26,AUX27,AUX28,AUX29,AUX30,AUX31,FL,FR"
      }
    }
  }
]

You have to change two things here:

• Replace {YOUR-BUS-ID} with the bus-id of your device

• Change the content of audio.position to reflect the output channels on your device.

• In the example above, FL and FR are actually AUX32 and AUX33. Which is the headphone jack on the Digiface USB (Channels 33/34). This is where i want my audio to play from.

• If you want to play your audio through Channel 5/6, you would replace AUX4 and AUX5, with FL and FR

Save the file and restart and all desktop audio should now play through your designated channels.

You are most welcome - even if i‘m late to the party.

I just moved to Linux over the weekend. Everything was smooth sailing until i tried to get my RME Digiface USB to behave normally. It took me essentially 3 days to get it to behave in an acceptible manner, so that i can do atleast basic audio things without much trouble.

It‘s fine for me now, since the all-day move to CachyOS was mostly for software development.
I still dual boot to Windows 11 for anything audio related that needs to be taken serious.

So yeah, i totally understand you.
I left it here mostly so that anyone that runs into the same issue in the future (may even be myself at some point again), will find the info if they ever need it.