Help with balena-sound and usb sound card configuration

I found balena etcher great. I liked the project suggestions. I decided to give a try to balena-sound. I have a raspberry pi zero and several usb sound cards. I do understand that the Digital Audio will provide better sound, but I have these USB adapters.
Balena-sound is working. I plugged and HDMI cable and the audio was working on the TV. The USB adapter is shown in alsamixer.
I have been looking different sources on how to configure alsa to use one adapter as default sound option. As balena-sound is a minimal installation there is a lot of configuration files that are not there. So I found some post suggesting about adding lines or editing mpd.conf .asoundrc or /etc/asound.conf but there are such files.
I tried some years ago some command line sound stuff and in the end I gave up.
I think that will be nice to have some tips to this setup as USB adapters are cheaper that a Digital Audio Hats. Even I am considering getting and HDMI to VGA adapter with stereo connector output. It is also cheaper than de Digital Audio.