I just finished a post on how to setup SVXLinux on raspberry pi. I’m thinking that you may be needing to disable the audio devices that you’re not using so that WSJT-X has no choice but choose the correct audio device.
What I feel could be relevant part:
Configure DigiRig
We want to configure DigiRig to show up as /dev/hidraw0 and have correct permission 666 so that the server as the raspberry pi starts up and gets ready to run the service the hidraw device is in the correct state.
Create a file in /etc/udev/rules.d I made mine 98-digirig.rules
SUBSYSTEM=="hidraw", ATTRS{manufacturer}=="C-Media Electronics Inc.", ATTRS{product}=="USB Audio
Disable Raspberry Pi Audio
Edit /boot/firmware/config.txt
Add # in front of line reading dtparam=audio=on
Update “dtoverlay=vc4-kms-v3d” to “dtoverlay=vc4-kms-v3d,noaudio” to disable HDMI audio.
Full Post: How to use DigiRig Lite with SVX Link