Hi Ed - just installed the beta driver for my AXR4U on an M1 MacBook Pro running Ventura 13.3.1. Install went well with activation and restart. DSPMixFX is working and controlling the AXR4U. Working in Cubase 12 with no issues so far to note.
I use 4.0.2b with Sonoma 14.0 for the UR22 without problems on an M1 Macbook Air.
Uninstalled the previous driver, installed the beta driver - then upgraded to Sonoma.