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?
Unless you have a seedbox, I’d still use a VPN on private trackers. You don’t want to expose your actual home IP address - anyone can see it when you’re torrenting (in the peers tab). You are correct that most companies that DMCA aren’t following private trackers and therefore it’s unlikely that you’d get a “love letter” but again I’d use a VPN for your home ISP.
As for getting into private trackers, there’s an OpenSignups community here. Otherwise, you have to usually know someone with invites to get in.