xset led 3,
xset led off,
xbacklight -set 00,
sudo find /sys/devices/platform/ -name leds returns nothing, so I couldn't try that.
sudo find /sys/devices -name leds returns
sudo echo '0' > /sys/devices/pci0000\:00/0000\:00\:1c.5/0000\:3f\:00.0/leds/phy0-led/brightness returns permission denied (yes, even with sudo).
sudo xmodmap -e 'add mod3 = Caps_Lock' returns error
X Error of failed request: BadValue (integer parameter out of range for operation)
Major opcode of failed request: 118 (X_SetModifierMapping)
Value in failed request: 0x17
Serial number of failed request: 11
Current serial number in output stream: 11
So, I pretty much just copied and pasted a bunch of solutions from stack overflow, and so far nothing has worked, although, this, I believe should be a very simple thing to do.
I'm on a Lenovo Yoga 720, running ubuntu 18.10.