Piracy: ꜱᴀɪʟ ᴛʜᴇ ʜɪɢʜ ꜱᴇᴀꜱ

Jellyfin

to answer your questions (to the best of my knowledge):

Who creates accounts: You create the accounts and give it to them, simple admin dashboard

How access works: its a web server, you configure listening port, that goes through your public facing router to your vpn router then to your torrenting rig that is hosting jellyfin once you can access it, everyone else with access to thr public facing router can by simply entering the ip:port or domain.

There are also clients for some devices, iOS needs a little work last i heard (a few years ago) Android is good to go TVs it depends, some have some dont They connect the same way through ip:port and then login

Rotating ports might be a pain, as you have to input the server ip:port then login on the client every time that changes, if i were you i would setup nginx/nginx proxy manager or something to keep my ports local and put only nginx at the front.

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it handles my anime, tv show, movie, and music collection pretty well, I have tens of thousands of songs, thousands of episodes, hundreds of shows.

Now to the issues; most recently playlists (as in i faced the issue yesterday), theyre finicky as fuck if you want to migrate from the instance they were created on to a new one.

Performance, the ui lags (usually when managing watched status or editing large numbers of items) I saw their focus for v12 was performance so that might change

jellyfin mpv shim (if you want to use mpv on desktop) sometimes just stacks everything you click, so you want to seek forward? no, it waits until something then replays all your seek commands

I havent tried Plex nor Emby, but I heard Plex handles remote sharing so you can access your server from outside the home network, but they have an expensive sub/lifetime payment.