I created and curated this list on Reddit, but as I've switched over here due to Reddit not giving a shit about the end-user, I figured I will bring the list and keep it updated here instead.
To add a plugin repository, from the homepage simply navigate to 'Dashboard' in 'Admin', Select Plugins in 'Advanced' and finally select 'Repositories' at the top. Below is listed each repo, and each plugin currently provided by each, including a brief description. (Duplicates across repos exist, some repos provide later versions etc)
Official Jellyfin Stable - https://repo.jellyfin.org/releases/plugin/manifest-stable.json
Bookshelf: Supports several metadata providers and options for organizing your collection
Fanart: Scrape poster images for movies, shows, and artists in your library
IMVDB: Metadata from IMVDB
Kodi Sync Queue: Tracks media changes while Kodi clients are offline to decrease sync times
LDAP Authentication: Authenticate users against an LDAP database
NextPVR: Provides access to live TV, program guide, and recordings from NextPVR
Open Subtitles: Download subtitles for your media
Playback Reporting: Collect and show user play statistics
Reports: Generate reports of your media library
TMDb Box Sets: Automatically create movie box sets based on TMDb collections
Trakt: Record your watched media with Trakt
TVHeadend: Manage TVHeadend from Jellyfin
InfuseSync: Track media changes while Infuse clients are offline to decrease sync times when logging back in
Cover Art Archive: MusicBrainz Cover Art Archive
TheTVDB: Get metadata from TheTvdb
AniDB: AniDB metadata provider
AniList: AniList metadata provider
AniSearch: AniSearch metadata provider
Kitsu: Kitsu metadata provider
TVmaze: Get TV metadata from TVmaze
Webhook: Sends notifications to destinations via webhooks
OPDS: Provides an OPDS book feed
Session Cleaner: Removes old sessions (devices)
VGMdb: Adds support for VGMdb to music libraries. Can provide both images and metadata for artists and albums
Simkl: Scrobble to Simkl
Subtitle Extract: Extracts embedded subtitles
Danieladov - https://raw.githubusercontent.com/danieladov/JellyfinPluginManifest/master/manifest.json
Merge Versions: Plugin that automatically groups every repeated movie
Theme Songs: Plugin that downloads theme songs for your media
Skin Manager: Helps you download and install various skins for Jellyfin
Simoni - https://simoni.dev/jellyfin/repo.json
M3U Editor: Edit Live TV M3U channel lists
Imaginaryupside - https://raw.githubusercontent.com/imaginary-upside/JellyfinJav/master/manifest.json
JellyfinJAV: JAV metadata providers for Jellyfin
Shemanaev - https://raw.githubusercontent.com/shemanaev/jellyfin-plugin-repo/master/manifest.json
MyShows: Scrobble watched media to Myshows.me
Webhooks: Supports couple of webhook types including Plex
Media Cleaner: Delete played media after specificed time
Oddstr13 - https://mirror3.openshell.no/jellyfin/plugins/unstable.json
Anime: Manage your anime from Jellyfin
Bookshelf: Supports several different metadata providers and options for organizing your collection
Cover Art Archive: Metadata from cover art archive on MusicBrainz
Email: Send SMTP email notifications
Fanart: Scrape poster images for movies, shows and artists in your library
Intros: Display flashy intros before media
Kodi Sync Queue: Sync all media changes with kodi clients
LDAP Authentication: Authenticate users against an LDAP database
Missing Episode Provider: Provides metadata for episodes missing from your collection
NextPVR: Live TV Plugin for NextPVR
Open Subtitles: Download subtitles for your media
Playback Reporting: Collect and show user play statistics
Trakt: Record watched media with trakt
TVmaze: Metadata from TVmaze
VGMdb: Metadata from VGMdb
Pushbullet: Pushbullet notifications plugin
Pushover: Send notifications via pushover
ServerWMC: Live TV Windows Media Centre plugin
Slack Notifications: Get notifications via Slack
Template: Plugin Template presumably for developers
TMDb Box Sets: Automatically Create movie sets based on TMDb
TVHeadend: Manage TVHeadend from Jellyfin
MusicBrainz: Metadata from MusicBrainz
TheMovieDb: Metadata from TheMovieDb
OMDb: Metadata from OMDb
Reports: Generate reports of your media library
TheTVDb: Metadata from TheTVDb
Auto Organise: Automatically organize your media
Kitsu: Metadata from Kitsu
AniDB: Metadata from AniDB
AniList: Metadata from AniList
AniSearch: Metadata from AniSearch
MrTimscampi - https://raw.githubusercontent.com/MrTimscampi/jellyfin-repo/master/manifest.json
Apple Music: Plugin provides album and artist images from Apple Music
Jesseward - https://jellyfin-repo.jesseward.com/manifest.json
LastFM: Plugin for LastFM scrobbling
ShokoAnime - https://raw.githubusercontent.com/ShokoAnime/Shokofin/master/manifest.json
Shokofin: Metadata for anime from Shoko
ShokoAnimeUnstable - https://raw.githubusercontent.com/ShokoAnime/Shokofin/master/manifest-unstable.json
Shokofin: Metadata for anime from Shoko
Lyarenei - https://raw.githubusercontent.com/lyarenei/jellyfin-plugin-listenbrainz/master/manifest.json
Listenbrainz: Plugin for Listenbrainz music scrobbling
Linfor - https://raw.githubusercontent.com/LinFor/jellyfin-plugin-kinopoisk/master/dist/manifest.json
Kinopoisk: Metadata for mostly russian media from Kinopoisk
K-matti - https://raw.githubusercontent.com/k-matti/jellyfin-plugin-repository/master/manifest.json
SMS Notification: Plugin for SMS notifications
NapiSub: Plugin for polish subtitle downloads
PhoenixAdult - https://raw.githubusercontent.com/DirtyRacer1337/Jellyfin.Plugin.PhoenixAdult/master/manifest.json
PhoenixAdult: Metadata provider for Adult content
AnilistSync - https://raw.githubusercontent.com/ARufenach/AnilistSync/master/manifest.json
AnilistSync: Scrobble watched media to Anilist
Jellyscrub - https://raw.githubusercontent.com/nicknsy/jellyscrub/main/manifest.json
Jellyscrub: Smooth mouse-over video scrubbing previews
IntroSkipper - https://raw.githubusercontent.com/ConfusedPolarBear/intro-skipper/master/manifest.json
IntroSkipper: Automatically detect and skip intros in television episodes
n0tflix - https://raw.githubusercontent.com/n0tOdd/n0tFlix/main/Manifest/n0tFlix-Manifest-Template.json
Addic7ed: Downloads subtitles from Addic7ed.com
NRK: Gives you access to all the content from https://tv.nrk.no
TvSubtitles: Downloads subtitles from TvSubtitles
Yifi: Honestly not sure about this one
YoutubeDL API: An API for using youtube-dl to collect streamable links from around the web, for making faster channels
TMDb Trailers – https://raw.githubusercontent.com/crobibero/jellyfin-plugin-tmdb-trailers/master/manifest.json
TMDb Trailers: Watch trailers from TMDb
Subbuzz – https://raw.githubusercontent.com/josdion/subbuzz/master/repo/jellyfin_10.8.json
Subbuzz: Download subtitles from various sites
CherryFloors – https://raw.githubusercontent.com/CherryFloors/jellyfin-plugin-cinemamode/main/manifest.json
Cinema Mode: Enable Cinema Mode with local trailers and pre-rolls
MetaTube – https://raw.githubusercontent.com/metatube-community/jellyfin-plugin-metatube/dist/manifest.json
MetaTube: Metadata Tube Plugin for Jellyfin/Emby
Ankenyr – https://raw.githubusercontent.com/ankenyr/jellyfin-plugin-repo/master/manifest.json
Smart Playlist: Create automatically updating playlists based on rules
YoutubeMetadata: Pull YoutubeMetadata from info.json or YoutubeAPI
Ani-Sync – https://raw.githubusercontent.com/vosmiic/jellyfin-ani-sync/master/manifest.json
Ani-Sync: Synchronize anime watch status between Jellyfin and anime tracking sites
NOTE – I am not the author of these, I simply collected them and listed them here so people have an easier time accessing them in the future! They may not work.
Also, if you're the author of one of these repos and wish for it to be removed, just shoot me a DM and let me know.
Most welcome!