I spent a lot of time trying to design a device like this with magnets as a kid, because my grandpa was interested in the idea in a kind of humorous sense, semi believing that it was possible, and I still have some interest but I don't think it's actually possible. I think these are all parlor tricks that they're putting on the Internet to mess with people. If it was so easy that you could just do it with a basic computer fan on your desk in a few minutes, there would be countless commercial examples and people would be generating power at their house using devices. if you could do something like this in a few minutes with some basic garbage on the desk, imagine the kind of power you could generate with a few thousand dollars of expensive parts and highly efficient fly wheels, neodymium magnets, and a closed vacuum housing. You could produce free electricity in your garage.