I’ve read on reddit I think that if you are torrenting using a private tracker you’re gonna be fine even without VPN. The question is: isn’t the tracker is just a server that leads my torrent client to the pieces of the file on the seeders? And the connection between me and the seeders is p2p, isn’t that type of connection is what makes your ISP snitch you? So what is different about private trackers? And where to find them?
I think the OP’s question is better worded on the second point as “What is preventing a copyright holder from joining a private tracker?” The answer to that is nothing. In theory, invites would only be handed out to trusted individuals, but the reality is you can just ask for invites and people will give you them.