Search for portable Jellyfin media server projects. It looks like there's a few out there.
If you're going to use this in a car, it needs to be as simple as plugging in a single device and powering it on. An over-engineered solution is going to quickly turn into a headache.
It was probably incompetence more than malice but T-Mobile customer service incorrectly told me multiple times that I was not allowed to pay off my phone balance early to unlock it. I'm on US Mobile now and I'll never go back to postpaid.