Originally runs eWeLink software so it has to be flashed over serial. Plastic case is disassembled without any screws. The wi-fi module has a SMA-C01 sticker on it and the module PCB is marked SM-001 v1.0 2018-11-14.
A lot of GPIOs are broken out at the bottom of the module but only some are soldered to the main PCB. TX and RX have no solder applied!
Flashing procedure is typical for this kind of devices. Keep the button pressed while connecting to your USB-to-serial adapter. Flash latest tasmota.bin using Tasmotizer!.