I recently upgraded my TV to a 4K Oled LG C1 from a Panasonic 1080p Plasma. I watch films via MKV files stored on a USB Pen connected to a Smart Blu-Ray player. This was connected to my Yamaha RX-V377 AV Receiver through the ARC on the blu-ray 1080p player.
Since I don't really use Blu-Ray...