Hello Andrew,
Thank you for your inquiry.
Is there an option to disable local echo for the command-line version of RTTClient on OSX? I check the manual and such and I didn't see one ... but I am well aware that sometimes things are so obvious that they get glossed over.
This options does not exist currently and it is not planned to add that feature.
Alternatively what you can do is to use any third party telnet client that offers that option and connect with localhost:19021 (more information in the J-Link User Manual).
If that option doesn't exist, is there any chance it could get added? And is there any chance of a GUI for OSX, like there is on Windows? I am using Ozone now, but the RTT terminal that is there isn't too useful since it is line-oriented, rather than character by character (for when the target has a "real" terminal implementation, for tabs, backspace, etc)
A GUI version for OSX is not planned currently. But i suggest you try out our IDE Embedded Studio which comes with a character based terminal which can be used in the way you described.
More information can be found
here.
Best regards,
Nino