I’ve been using Streamfab to download niche shows I’ve purchased through prime video that I couldn’t find anywhere else. It’s expensive af, but there’s a crack for it.

b64: aHR0cHM6Ly9rby1maS5jb20vaS9JVzdXNkxKN0Iw

Sonarr and Radarr automatically scan for TV shows and movies (respectively) on indexers you set them up with and send them to be downloaded with your client. You can use tools like Prowlarr or Jackett to help integrate various indexers without native support into Sonarr and Radarr, like private torrent trackers.