Just started evaluating Royal TSX as a replacement for a competing product. So far so good, but did run into one snag: Telnet sessions don't detect screen width, and wrap at the standard column count. This was essentially a deal breaker for me, as I have to use telnet to manage a string of older equipment, and line wrapping is going to kill me.
I filed a support ticket and they suggested installing the inetutils homebrew package. You can then specify the new telnet binary in preferences, connection types, terminal. This did fix the line wrapping problem, but introduced an oddity: Send Text triggers stop behaving the way I expected.
With the embedded telnet, sending "\n" actually sends "\r\n", so the triggers I had to send username and password worked with just "\n". After switching to the inetutils brew package, it would send only "\n", which is fair since that's exactly what I told it to do. Updated my triggers to use "\r\n" and all is well again.
(The path to the telnet binary installed by brew is "/usr/local/bin/telnet" in case you don't have a lot of experience with it.)