Original firmware works with AzpenHome app - so this appears to be a clone. The Socket 2 Me plugs seem to only be purchasable in bulk as customized sockets (for businesses etc.). Button works for plug relay, but there is a second “relay” for the USB power as well.
3.3v, ground, tx, rx, and gpio0 are all broken out on the board to a block of header pins. They are also printed on the reverse side. The button is not tied to gpio0, so you have to use the header pin. The header pins were to tight to get more than 2 jumper wires side by sine - not sure if the header pins or jumper wires are the culprit.