I finally have a properly working QDX (v4). Running fldigi, I get audio from the QDX. The audio levels are initially low, so I can run flrig to boost the levels. Seems to work fine. But I still cant get audio using WSJT-X, with or without flrig.  I asked about this a week ago, but that was before I had a properly working QDX. I'm now past that issue.

Mac OS: Ventura 13.0.1
WSJT-X for Mac: 2.6.0-rc4
fldigi: 4.1.23
flrig: 1.4.7.46

In the Settings->Audio tab, I have Input set to "QDX Transceiver".
In the Settings->Audio tab, I've tried Rig as "FLRig FLRig", "Kenwood RS-440S" and ":Kenwood 480". The Kenwood options work ("Test CAT" goes green) only if I stop flrig, which makes sense.

What's the trick to get the audio routed to WSJT-X on the Mac?

Nevermind! I downgraded to WSJT-X 2.5.4 and it seems to work just fine!

   ...doug, K6DRK