I'm not sure if the piracy megathread or FMHY megathread cover the *arr stack specifically, but they have lots of information so I'm recommending them broadly for anyone wanting to ingest information about piracy.

Regarding what the arr stack even is:

Tldr, you set up a list of public and/or private trackers in Prowlarr or Jackett. In Radarr and Sonnar you set up movies and shows respectively that you want to keep track of. Rad/Sonarr check those trackers for releases for your tracked media matching criteria (like resolution, size, language, etc).

When it finds a matching release, it sends the torrent file or magnet link to your torrent client to download. When it finishes, Rad/Sonarr hardlink or copy the file to a library location and organize/name them according to rules you set.

You can point Jellyfin or Plex to that library location and all the media will be organized so it can easily figure out what media is there and grab metadata for it (cover images, description, ratings, etc). Then you can watch that media through Jellyfin/Plex or an app that plugs into them.

The *arrs also work with usenet if you'd prefer that over or in addition to torrenting with a vpn.

The servarr wiki and the trash guides have a lot of info on what the various pieces do and how to set them up. I didn't strictly follow them but I've browsed them to get ideas on stuff like custom formats and such to get sonarr/radarr to automatically download and upgrade towards the codecs/quality that I prefer.

Personally I run Plex+jellyfin side by side to start, then sonarr/radarr/lidarr to download and organize TV/movies/music, with prowlarr to auto setup torrent sites into sonarr/radarr/lidarr, with a transmission+VPN docker container connected to each of the same 3, and finally an overseerr web ui that my friends can log into to submit requests to be auto downloaded by sonarr/radarr.

It's a lot to set up at once, but I started out with just Plex like 10 years ago and I've slowly added each container as time went on so it's only like a couple weekends a year where I tinker with it or do a migration to a new box as I moved from place to place and had different spaces available for my gear. Start with just a Plex and/or jellyfin server, you can tinker with sonarr/radarr without using it to auto download at the start. It's still super useful for renaming / organizing files, and you can only add certain folders if you don't want it to mess with a collection that you prefer to manually manage. Or create a new junk library folder to let it run amok with until you have it configured to your liking. Add in a torrent+VPN/Usenet downloader container to get it auto downloading when you're ready, and when you get tired of accepting requests personally from friends, an overseerr (for Plex) or jellyseerr (for jellyfin) container they can log into with using their existing Plex/jellyfin login to have their requests automatically forwarded to the appropriate *arr app and you'll have a fully automated low or no touch piracy setup. One of these days I'll also get bazarr up and running to make it easier to grab subtitles too since every once in a while I download something obscure and the only torrents for it dont have subs so I manually grab them from opensubtitles or something. It feels pretty magical though when you've requested a series and throughout the week, you see new episodes just pop up on the recently aired/added row in Plex/jellyfin within an hour or two of the episodes airing.

https://wiki.servarr.com/

Their quick start quides are pretty good.

I'd start with Radarr (Movie manager), add on Prowlarr (indexer manager), then expand from there. Once you've learned Radarr, the others are very similar.

After that, look into a reverse proxy along with a domain name: Nginx or Apache are the two I hear about most. I use nginx myself. This will let you access services using easily readable names (sonarr.example.com) instead of having to remember the ip+port combinations of each service (192.168.0.200:8096) as well as add https if you're going to be exposing things like emby/jellyfin/plex publicly.

A domain can be purchased/rented from a public registrar to point at your public IP, but you can also use them entirely within your own LAN for free if you setup a local DNS server. I just use pihole for this: easy to setup+use, while providing DNS based adblocking for the whole network.

I don't mind answering questions or providing clarification where I can. :)