Well, along with some help from third party program, it can be done effortlessly. Since Apple TV 4K can't support MKV format, just convert 4K MKV to Apple TV 4K friendly MP4, M4V and MOV formats and then simply sync with iTunes. If you lacks interest for Infuse or Infuse doesn't work for you, here is another option for you. Using video converter to transcode 4K MKV to Apple TV 4K friendly format We can perfectly stream 4K MKV/H.265 media from Synology to the Apple TV 4K by using Infuse 5.

It's also officially certified for Dolby Digital Plus and DTS/DTS-HD audio playback, a claim few other media player apps can make.

In addition to Apple-sanctioned MP4, M4V, and MOV formats, Infuse can play MKV, AVI, WMV, and a host of others, all with smooth hardware-based decoding in up to 4K resolution. It allows iPhone, iPad, and Apple TV owners to play nearly any video file without conversion and stream content stored on cloud services or networked storage complete with subtitles, AirPlay, and Google Cast support. To play 4K MKV on Apple TV 4K, one recommendation is to use Infuse 5.

But that doesn't mean there isn't a solution though! Here we put together 2 possible solutions for you. They are currently working on getting 4K content to play when using MKV container as well. The Plex team 'forgot' to update the Apple TV profile to support direct streaming when playing 4K material in the MP4 container, as this is supported out of the box. Based on our testing and some guys' feedback, Plex server on Apple TV 4K does yet not support 4K. There is a hot topic on Apple and Plex forum: streaming 4K MKV to Apple TV 4K via Plex server is not working.

I use PlexPy while the MKV video format is being streamed to the ATV 4K to determine whether or not transcoding is taking place.' When I do that, the Plex server perform transcoding. 'There is no way for me to either 'directplay' or 'directstream' a 4K MKV/H.265 media from my Synology Plex server to the Apple TV 4K Plex client (all my movies are stored in my Synology). Stream 4K MKV/H.265 to Apple TV 4K via Plex Not Working- Solved

Apple tv plex 4k