Should have clarified that this is for specifying the device on the command line. (But the related bug makes that clear.)

Also, just realised I've only tested this on linux and have assumed that a slash inside quotations ("\") will be interpreted the same way on the command line of each platform. (Does anyone know if that holds true on the windows command line?)

Thanks guys! ran rtmode from command line, but I'm still getting that error about unescaped commas: "/usr/local/bin/jacktrip -C 47.95.31.155 --rtaudio --srate 48000 --bufsize 128 --audiodevice "Rogue Amoeba Software, Inc.: Loopback1","Rogue Amoeba Software, Inc.: Loopback1" -o 0 --sendchannels 2 --receivechannels 2 -q auto -r 1 -b 16 -z --bufstrategy 3 --udprt -K "ken5"
ERROR:
Found multiple unescaped commas in the --audiodevice argument, cannot parse reliably.
Exiting JackTrip...

chatGPT'd:
In command-line tools, you can escape a comma by preceding it with a backslash ():
--audiodevice "device_name\,extra_info"

so I tried that command line with the "\" character before the comma, and it worked!

works ok on mac

did you try Rouge Amoeba's Loopback ?

device name reads as:
"Rogue Amoeba Software, Inc.: Loopback1"