sonoff

compiled Sonoff-Tasmota from https://github.com/arendst/Sonoff-Tasmota.git (read directions there) and save the .bin somewhere easy to get to

rip the chip off your arduino, you're going to use that bish as an ftdi adapter

wire it up like this:

arduino     sonoff pins
3.3v        pin 1
RX          pin 2
TX          pin 3
GND         pin 4
(empty)     pin 5

to put the sonoff in flash mode, the button needs to be held when you connect the 3.3v

i soldered a header to one but got lazy on the others and just held the header at an angle to power it while it flashed

grab esptool via pip "pip install --user esptool"
run this where your usb device is /dev/ttyACM0 (this the case when using an arduino as an ftdi, otherwise it's probably /dev/ttyUSB0)
esptool.py -p /dev/ttyACM0 write_flash --flash_mode dout 0x00000 sonoff.bin