What’s the best device to play back either downloaded 4k content or ripped 4k blu-rays at the highest possible quality?

Ugoos am6b+ running CoreELEC.

https://docs.google.com/spreadsheets/d/1jBIGF8XTVi9VmDBZ8a5hEyongYMCDlUiLHU9n1f_S74/preview/sheet?gid=427220017

For something with less tinkering required and compatibility with streaming services, get an Nvidia shield or AppleTV 4K and run Plex or Jellyfin.