Sharing magnet links via Nostr is good, since it eliminates the centralization of websites like Pirate Bay.

The next major problem to address the fact that trackers expose all users in the swarm, especially if an ISP gets access. I see two possibilities: (a) organize private trackers via Nostr, using zaps and web-of-trust for admission. Or (b) somehow eliminate per-torrent trackers entirely, perhaps through a mega-swarm, in which users seed/leech more torrents than what they actually want (I am not sure how this would work, so it might not work, but it might be worth investigating).