Also to list my favs here that haven’t already been mentioned:

• torrents-csv - I made this so I’m partial, but its an open source csv file of all popular torrents, with a search engine. Scrapes periodically from TPB and several other popular sites.
• ThePirateBay
• MagnetDL
• SkyTorrents
• 1337x

rarbg.to is my favourite one. There have been a few things that I wanted that I found there but could not find on thepiratebay.org. Also, significantly less adds and better up-time.

I usually use https://openpirate.org

I use qbittorrent, it has a built in search engine and you can add plugins to it, so that it searches through multiple websites.

• Classic, works decently for music: https://rutracker.org
• The anime generalist one is: https://nyaa.si/