I would say either private torrent trackers or usenet. Later I never tried.

I never had a problem with "garbage" on private trackers, and if they are "nuked" fairly quickly.

Both torrent and usenet can be automated. (Sonarr, radarr etc.) If you want to watch a specific series, new episodes will be automatically downloaded, added to the torrent client, maybe moved and renamed and you get a ping your discord server / telegram / whatever.