Are you saying, theoretically if I had 100s of TB (I don’t… yet!) on mounted drives (local or NFS shares), I could back it all up to Crashplan, and keep the retention as long as the files still exist on my device(s)? Sounds amazing, but what’s the cost of restoring the data? They’re not being very loud about that part on their website.

When I cast from the Jellyfin app on my phone (or the webapp) (to either the Jellyfin app on my Android TV box) or to Kodi (through Jellycon/Jellyfin addon or DLNA), the content is playing independently of my phone. This means that if I disconnect from the device I’m casting to in the Jellyfin app, the content will keep playing. It’s not streaming through my phone, but I can reconnect to regain remote control. I guess it’s the same case for Linux clients. If not, you can use Kodi with Jellycon addon (and not the Jellyfin addon, since that will sync the library to Kodi, which is unnecessary here). You will need a screen to set it up, but once that’s done + auto-launch Kodi at boot if you wish to, it will work headlessly if necessary as a client to cast to. Another reason to use Kodi is the very wide variety of formats it supports.