Anytone AT-6666 has a USB connector but from the manual it doesn’t appear that it is used for the digital modes like in case of more advanced transceivers. There are no other accessory connectors so we’ll have to collect audio/ptt from mic and headphones jacks.
If I had to guess, the connector is GX16-6 (needs confirmation)
Based on this schematic, the Digirig cable would be:
GX16-6 pin 1 (MODULATION) → 3.5mm TRRS ring 1 (RIG_AFIN)
GX16-6 pin 3 (TX) → 3.5mm TRRS ring 2 (PTT)
GX16-6 pin 5 (GROUND) → 3.5mm TRRS sleeve (GND)
3.5mm TRS sleeve → 3.5mm TRRS sleeve (GND)
3.5mm TRS tip → 3.5mm TRRS tip (RIG_AFOUT)