I’m going to keep it brief since documentation exists for all of these if you want to understand how they integrate.

Media server: Plex. Alternatives exist(emby, jellyfin), but Plex just works on nearly any client.

Content: Radarr(movies), Sonarr(TV shows). Automated content grabbers for usenet/torrents.

Subtitles: Bazarr

Requests: Overseerr

Several guides here: https://trash-guides.info/

Hopefully this can get you started and some others might chime in with more detail.