No audio using CMI6206 USB device in 7.1 mode (but works in 5.1 mode)

Could anyone advise me on getting audio to work with 7.1 channels using the following device:

Noblik 7.1 Sound Card Usb 2.0 Sound Card Cmi6206: Amazon.co.uk: Electronics

I am using a Rpi4 on the LibreElec 9.2.1. Setting the number of channels to 5.1 works as expected. However I get no audio if i set it to 7.0 or 7.1. Additionally, when set higher than 5.1, videos play for a few seconds (silently) then freeze. I can stop the video, return to the settings and switch to 5.1 to get the video to play perfectly.

I plugged the audio device into my x86 LibreElec machine (9.2.2) and it works perfectly in 7.1. I tried copying the audio settings exactly from the x86 to the pi but no audio configuration seems to make any differene.

I have attached a log file where I switch from 5.1 to 7.1 and then attempt to play a video.

Any guidance would be welcome.

Log file: hastebin

The video file is opened on line 475.

Quote from blueribb

HD Audio for rpi4 still not available

Thanks blueribb but I'm not trying to use passthrough which I think is what you mean?

I just want to use the USB audio device in 7.1 mode. If I have it set to 5.1 I can decode all the standard 8-stream files and they are downmixed to a 5.1 correctly.

Does the Pi4 simply not support USB->7.1 Analogue at present?