A quick look showed me that qbittorrent doesn't have a dht crawler to create an index (please correct me if I'm wrong). Basically you can use bitmagnet to create a huge index so you can find any file you desire (you're making your own piratebay in a sense) and then use qbittorrent to actually download it as you normally would.

Bitmagnet is something you'd run on a server as it indexes everything and takes a while to become useful. (after two weeks you should have more magnet links than piratebay). Depending on your country make sure to route it through a VPN