“Shelly One” is just one example of several (claimed) open source products produced by a company called Shelly who are based, not as you might expect in China’s mega technology city of Shenzhen but in Sofia, Bulgaria. Shelly are not new and there are plenty of videos out there about their products – so I won’t bore you with the usual stuff. I call them “Shelley” but I note that the box and their web interface footer state “Allterco Robotics Ltd”.
Suffice it to say that they make (or perhaps re-badge in some cases? Just a guess) quite a variety of products from relay switches, through energy switches to smart RGBW lights, flood sensors, temperature sensors and more.