Turns your TV into a YouTube/Netflix/Spotify/Hulu, and the remote-control is your phone.

If by "arbitrary 1080p content", you mean a collection of media files of your own, I'd get a Raspberry Pi 3B+ kit for $50, plug in a large external HDD or two, and setup a Plex server.

There is the Pi 4, which once all the parts and shipping are put together about $80. Though, eh.. imho it's better if you get one of the Intel Nucs. They can be had for around $200 and are quite good.