Thanks for the ideas! I figured out something very similar the other day. ‘stty sane’ to the USB device resets the serial port and turns off the PTT. It’s annoying that it turns on, and I can’t seem to change the defaults, but at least I can use the radio with the Mac!
Next issue is the LD-5 and hamlib. Seems like the TS-2000 emulation isn’t close enough for hamlib. Booo! I can control the PTT with wsjt-x on the Mac, but not the VFO via cat control due to the incompatibility with hamlib. Closer though!