The most elite trackers perhaps.

Trackers on /r/opensignups ? Nah they open their doors to the public every now and again.

Would not recommend it to anyone who can’t dedicate a seed box or machine uploading torrents most hours of the day every day. It’s possible to do it without those but difficult. With them it’s merely a matter of using free leech and building a buffer up as well as taking advantage of points systems to get free upload just for keeping torrents seeding even without uploading.

If you only ever grab free leech then all you have to worry about is meeting seed time and activity requirements like logging in every 90 days.

An old computer with an external drive. A raspberry pi, a nas that can run a BitTorrent client. Any would work if one doesn’t want to pay for a seed box. (Most trackers ban shared seed boxes though so you will have to get dedicated)