I used to use thepiratebay.org, but recently it seems the quality of the site has degraded.
I sometimes also use 1337xx.to , but that site seems to have a very small selection.
Note that I couldn’t find an answer to this question in the wiki + meathread, so if the answer is already there, please direct my attention to it 🙏🏴☠️
I just have a bunch of search addons for different sites directly in qBittorrent. I haven’t made a website search for a long time.