Warning! The “SERIES II” version is not ESP based and uses WB2S instead.
The WB2S can be replaced with an ESP8266EX, ESP-02S which is pin-compatible. However, this is quite envolved:
There are no screws and the 2 part shell is glued/welded together. To separate, find the seam at the back and very carefully use a sharp instrument to beak the seal.
In order to accsess the pads of the controller, the AC power pins must be desoldered.
Once the AC pins are fully desoldered the board can be fliped over and the WB2S removed and swaped for a pre-flashed and configured ESP-02S.
With the ESP installed properly and fully re-solder the AC pins, place the front cover back on, and use some glue to ensure it does not fall off.