So, what I have done, following your steps:
Downloaded the file you mentioned, directly, to avoid copy pasting problems.
Before doing any changes as you suggested, I entered the container, doing in the guest host:
docker exec -it rhasspy sh
and then
'# aplay test.wav
ALSA lib pcm_dmix.c:1108:(snd_pcm_dmix_open) unable to open slave
aplay: main:828: audio open error: No such file or directory
So two errors, the first recgarind the audio hardware problem, the send because I don’t have a test.wav file
OK, then exiting the container sh, returining to the guest host
$ pwd
/<…>/portainer/Files/AppData/Config/Rhasspy/files
Changed the owner to the user with docker permission, in my case it is docker_user
sudo chown docker_user asound.conf
Checked if the contents were OK
nano asound.conf
And it has the contents of the whole file as expected.
Create a new entry in my docker compose file, as you said:
– “/<…>/portainer/Files/AppData/Config/Rhasspy/files/asound.conf:/etc/asound.conf”
Launched the container, OK no errors.
Entering the sh of the container again
docker exec -it rhasspy sh
'# aplay text.wav
aplay: main:828: audio open error: No such file or directory
Now it only has the error regarding to no file found.
It doesn’t complaint about the hardware.
It seems I am getting somehere 
In the rhasspy UI, in PyAudio, I have more options now:
array, arraygain and cap
If I press test, still non gives me WORKING state
I was saying changing to arecord does the same, before writing this, but now it says WORKING
Default Audio Device (sysdefault:CARD=CameraB409241)
So it seems you helped me doing something right!!! Thank you!
As I am lost now, what would be the next steps to ensure this is working?
Using arecord?
What next?
Thank you very much for your help, your directions are straight to the point.
Hope my “documentation” also helps someone.
PS: I bought PS3 Eye for 1 euro at a used hardware store, hence using it