I set up Balatro in Wave Link to route to Wave Link Game, and noticed that there was no audio. Changing it to other virtual outputs, like Browser or Music, also produced no output.
I added System as one of the inputs, and noticed that I got audio back. Balatro seems to ignore any attempts to route the audio through a virtual cable, and will only play straight to whatever is set as the master output.
I imagine this could be replicated in similar software that has virtual audio, like Voicemeter.