Pipewire how to route two usb sound cards from mixxx into easyeffects

I am trying to route the output of mixxx into easyeffects.

I have two driveless usb sound cards, each one is affected to a deck output in mixxx.

mixxx is set to use alsa and I have pipewire-alsa installed so mixxx should be routed to pipewire, but:

easy effects fails to detect mixxx outputting an audio signal.
Helvum and qpwgraph both fail to detect mixxx, qpwgraph do detect the sound cards but not reliably while helvum does not.

when I switch to the internal soundcard and assign it to master output in mixxx, pipewire finds the card and everything works as expected.

how can I make pipewire aware of the usb sound cards, of mixxx outputting audio, and route both of them to easyeffects ?