I originally used some code from here - Adafruit Feather32u4 with Lora
With a couple of additions:
// Sleep radio
//USBDevice.detach(); doesn't work on 32u4
// Disable USB clock
USBCON |= _BV(FRZCLK);
// Disable USB PLL
PLLCSR &= ~_BV(PLLE);
// Disable USB
USBCON &= ~_BV(USBE);
// ATmega32U4 sleep
LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF);
// Reattach USB to have Serial working again
Found in RocketScream forum here. The most important bit being disabling the USB, which saved a lot.
I’ve also had some attempts at removing the voltage regulator and bridging the 5V/3.3V pins. (Note: that you really need to program via ISP after this)
Here are the results with the Adafruit code above:
I have been able to replicate the same power usage with LMIC lib. The only additions I’ve made to the TTN ABP example code is changing pins, adding LowPower lib sleep and disabling the USB with same code as above.
Hope this helps.