Use a VPN service with a proven track record to connect to a seedbox paid for with crypto, and download only from top-level private trackers. It's about as secure as you can get as a casual user.
In reality, though, a simple VPN is probably enough. Maybe not even that if you're in a country that doesn't give a shit.
It's nice to live in a country that doesn't give a shit. Where I am they'll reluctantly send you a letter because the media companies hassle them about it, but they hardly ever do more than that. A friend of mine got a letter and called his ISP, and they were just like "you should use a VPN or not seed so much, that's how they spot you" lol
Otherwise an open source client such qbittorrent or transmission on an open source os such as Linux with a VPN provider whose privacy policy you are happy with. The most important thing is to bind your torrent client to the VPN interface inside the torrent client settings.
There are more technical setups to automate parts of the process but learn to walk before you can run.
The invisible internet protocol. It's some version of the Darknet (like tor), but you can only communicate with hidden services through it (There are no exit nodes).
Because of that your IP isn't involved in transmitting the data.
It is an anonymity network similar to tor if you have heard of that. I would recommend playing around with i2p+ to get started with it. You should be able to get it from here: https://i2pplus.github.io/