What is the point of adding other public tracker? Is it to cross seed? Or just higher probability to connect to a peer?

I add a bunch I copypasted from a list somewhere

I don’t have direct answer to the question, but I generally don’t add public trackers to my (public) torrents. DHT/PEX usually works fine for me for finding seeds on the occasion that I do need something from public torrent sites.

I wonder whether adding additional trackers only increases the speed in which peers are found or whether it also substantially increases the likelihood of finding peers.

honestly… I don’t know what a tracker is, I just click the magnet button and qBitTorrent just downloads it
Is there something more I should be doing?

Doot for later