You need 2 indexers (in case one goes down temporarily) and two providers with different backbones - one primary and one to backfill if all portions of the file you want aren’t available on your primary.
Here’s a good overview of Usenet backbones. For example, Newsdemon with Eweka is a decent combo.
This all works best with an *arr stack + SABnzbd. *arr apps will connect to the indexers so you can find stuff to download when you search for something - for example, Sonarr for TV shows.
When a file that meets your requirements is found, Sonarr will download the nzb file and put it in a directory that SAB watches. SAB then downloads the file and puts it in “completed” directory that Sonarr watches.
Sonarr then moves the file to that TV show’s directory, which your media player (like Jellyfin) watches, and then it shows up there for you to enjoy.
If you get everything dialed right, it works perfectly and is super reliable.