Thanks for the responses. Latest tests: run rigctl from Terminal on both the Pi and Linux computers. Here's the example on the Linux laptop with the Pi result about identical:
~$ rigctl -m 122 -r /dev/ttyUSB0
Rig command: f
Frequency: 7070500
So I can read and control the uBitX as Yaesu FT-857 in rigctl and "see" it in CQRLog. But fldigi and flrig cannot see it.