Kinda cool, I was thinking about building a similar system, but based on NFC tags to load specific movies from my Plex server.

At least those are easier to acquire, and they can't get demagnetized :)

I do this but for music with Home Assistant. I haven't dug around much to see if it's possible to cast video from Jellyfin the same way. From what I read (and it's been a while) the Jellyfin API was more limited, but maybe that's changed by now.