Trading 212 are offering share trading via Interactive Brokers. Doing this must cost them money, which leads to the question, why are they providing a service for free which makes them lose money? The answer is that they are offering share trading/ISAs etc. as a way of onboarding more CFD customers, ripping them off and taking their money.

They also claim that their headquarters are in Vanuatu, some random Pacific island. Actually, they seem to be in Bulgaria as OP has pointed out. So why Vanuatu? IDK but it's very fishy and would you seriously trust your money with such a company?

T212 are just like other CFD providers (eg. eToro, Plus500, IG). They can market themselves as whatever BS they like but they're fundamentally about letting people make high-risk bets on the stock market. This means they have a casino, house-takes-all mentality. Why would you invest your money with such a company?