I wonder if your Teensy 3.6 is toast? Have you managed to program it?
(Before you program it the first time, it blinks when you plug it in, once you've program it, it won't do that unless of course you program it with a blinky program...)
I hooked up my Teensy 3.6 to my computer, and uploaded lightsaber.ino with no modifications.
Then I opened the serial monitor (Ctrl-Shift-M), which said:
No sdcard found.
ID: 916 volts 2.95 resistance= 279888.97
WS2811 Blade with 97 leds
Scanning sound font: font01/
The "no sdcard found" is normal, since (a) I have no sdcard inserted and (b) I haven't configured the SD enable pin correctly.
Note that this is with nothing connected to the Teensy except for the USB cable. (no prop shield)
After printing this, it hangs because it tries to talk to the sd card even though it's not there.
If I comment out #define ENABLE_SD, it gets a little further, but then it fails to talk to the motion chip, since that's not there either. So I comment out #define ENABLE_MOTION too. After that, it it doesn't hang anymore I and the chip responds when I type "help" in the serial monitor.
As for DAC0 -> DAC1, you have the right idea: Replacing DAC0 with DAC1 should work, but you should see things printed through
the serial monitor either way.