You can use any torrent client with search included. For example: qbittorrent, frostwire, etc…

Anyway check FREEMEDIAHECKYEAH! https://fmhy.net/videopiracyguide#torrent-sites

usenet is decentralized at server level. In theory all the servers have the same content. Currently everything is obfuscated because of the take downs - so you need an indexer (the users upload the nzbs to that website. Think of a nzb like a .torrent file.)