No surprises when flashing. Because I have no idea how to safely solder stuff directly on the chip, I just attached the 3V/GND on the back and held the TX/RX in place using my fingers. Worked without problems:
Here is another guide to flashing these, if you want to see more pictures: https://www.hackster.io/michael_zanetti/smartlife-tuya-wifi-light-switch-with-tasmota-and-nymea-09a7a6
Any finally, this is my esphome config for the 1-gang version: https://gist.github.com/tribut/24da88affbf0d57a6ad143edcf6b53d0
Have fun!