A first big thank you to John.
Installation successful but I needed an extra step in addition to those in the Readme:
The list of CAT ports does not appear to be extensible, so I made a symlink as follows:
cd /dev
sudo ln -s /dev/tty.usbserial-AD02DV1X ttyUSB0
then chose ttyUSB0 in the menu, then CAT worked fine.
73, Elwood, WB0OEW