Paul,
This is quite different to the problem I am seeing. I can start the Arduino IDE and edit programs, I can compile programs.
what I cannot do is download programs to the Arduino hardware.
I am using a genuine Arduino UNO and have the most recent version of the IDE loaded.
I have also used the most recent version of Catalina on the Mac.
If I compile and download a program using a windows PC and then connect the Arduino to my Mac I can get serial data from the Arduino to show up in a terminal session so I believe all the hardware is working fine.
The problem I am having is just the download to the Arduino.
I have been following a thread on github and it looks like this is related to the way the Arduino downloader works.
But so far I have not seen any solution for this issue.
Cheers
Peter