My first 2 GTIs (Suoer DB600 and DB1000) were the cheapest available Chinese products.
Completely safe, if there was no grid supply they didn't work.
I've never found any GTI that would work without a working grid supply.
As for needing a professional electrician, they came with a 3 pin plug to put in any nearby socket, same as every other available electrical device. Do you really believe all electrical equipment needs a professional electrician to put the plug in the socket?
Please link to one that is dangerous for sale on Lazada or admit you're posting misinformation.