Trying to run QU-Sb from VLC on a Raspberry Pi 4

Hi Folks

Here is my setup:
I have a main stage rack with a QU-Sb mixer controlled via an iPad Pro using an Apple AirLink Wireless access point. I have a Raspberry Pi4 running Buster that I use to switch patches from a setlist app that I wrote installed in the rack. My objective is to have a media player to play mp3s during the band breaks, controlled by our sound guy. I am trying to run VLC (because We can control it remotely via the iPad) on the Raspberry Pi using the QU-Sb as a sound card connected via USB. Unfortunately I cannot get any audio functioning. The raspberry Pi recognises the QU-Sb as an audio device and I can get it to play white noise using the procedure from this link:

So at some level the system is working but when I go into the configuration setup for VLC and select the QU-Sb as the audio output device (yes it recognises it), I get no audio!

This is the setup I have in VLC:

VLC ALSA Config Settings

I have two questions!

  1. Has anyone managed to get a QU running from VLC on Linux
  2. Does anyone know of an app that a) will run on linux, b) works with a QU and c) can be remotely controlled via an iPad(iOS)