Pick up a Nvidia Shield Pro 2019 on ebay. Connect an external hard drive through one of the two USB ports and run Kodi as your library manager. That should be all you need. Supports HDR, 4k, upscaling.
If you go that route, run a launcher for a more streamlined home screen. I’m running Projectivy Launcher because it was easy to install and does what I need it to, but there are other options out there.