qBittorrent is a free, open-source BitTorrent client without ads or bundled offers. Search plugins, RSS, and sequential download are built in. It runs on the major desktops. The protocol is legal. The files you share may not be. That part is yours.
The swarm sees your IP address. A VPN does not help until you bind qBittorrent to the VPN interface so a dropped tunnel cannot leak. DHT and peer exchange make you easier to find and also announce you to more strangers. Turn them off only if you know you are on a private tracker that does not need them. The search tab can find anything. It does not check whether you are allowed to fetch it.
Use it as the default client, after the bind-to-VPN setting. qbittorrent.org
In qBittorrent, set the network interface to the VPN adapter and turn on the option that stops traffic when that interface is down. Then pull the VPN and see if the download stops. If it continues, you are not done. Legal torrents exist and they still show your IP to the swarm. That is fine for a Linux ISO and not fine for a file you would not put your name on. The search plugin is not a lawyer.