Mike Sutherland <ve3uet@...>
I got this message and followed the instructions
I suspect you are not selecting the correct serial port device for CAT in WSJT-X. Your screen capture shows "USB", that is definitely incorrect. I would guess that /dev/ttyUSB0 is the right one, that would be a USB to serial interface.
You also need to add your user to the 'dialout' group to be able to access serial devices:
sudo adduser $USER dialout
You must log out your desktop session and log back in for that to take effect, or simply reboot.