Kind of luck based but you can read up online on how to get into private trackers. Some have open registrations which will get posted to places like here. Some are invite-only.

But Prowlarr lets you add a bunch of public trackers to cover most new stuff. I find that private trackers are better as archives for less popular stuff.

Use usenet over torrents. You're downloading the files from a server rather than peer to peer so you avoid the issue of not having any seeders. There is usually a fee associated with registering with a usenet provider and indexer, however, you can sometimes get a free trial or a limited number of "grabs" per day to test it out.

Earlier you could find temporary open trackers on r/opensignups
Now it's a bit more difficult.
Torrentleech is a good beginner tracker. Usually opens around Eastern, Summer, Black Friday or Christmas.

You could aso search "open signups torrent" online and try to find something with enough content.