It IS a fork of Emby, however, which is quite similar to Plex in how it behaves. Crucially, Jellyfin does not make you log into someone elses website for your own content. Don't you find that kinda weird about Plex?

But yes, the downside is the lack of smooth integrations. When I tried Jellyfin about a year ago they did not quite have Chromecast support nailed down, however as of now they've got a fully functional Android app and proper Chromecast integration.