“Jellyfin is pretty much a drop-in replacement for Plex Media Server’s core functionality.”
Plex started as a way to watch your own files. A decade later it pushes its own streaming catalog and premium tiers on top of your library. Emby went paid too. Jellyfin does the cataloging, metadata and transcoding for free. When the software you host yourself starts serving you ads, it’s time to host something else.