OSX 10.14.6 Arduino IDE unable to detect Mega

Arduino IDE should detect Arduino Mega on OSX.
I'm selling my macbook ASAP but i still want to get this to work. I am 100% certain this is a firmware issue and that apple products will continue to degrade.

I don't see usb tty i see usb cu (cu.usbserial-1410)
Serial Monitor works as expected, but cannot upload sketch:
```
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_getsync(): timeout communicating with programmer
avrdude: stk500v2_command(): failed miserably to execute command 0x13
avrdude: stk500v2_paged_write: write command failed
```

Reproduce the upload failure with Arduino IDE on OSX 10.14.6 using an Arduino Mega, noting that Serial Monitor works through cu.usbserial-1410. Start by tracing the IDE's upload path and the reported avrdude stk500v2 timeouts; done means the Mega is detected and sketches upload successfully.

Written by the indexing model from the issue text.