I'm thinking it would be great to mount a small Linux computer to the back 
of a TV and connect it to an HDMI port on the TV.  It could then connect 
via WiFi to a media server and show videos, photos, streams, etc. on the 
screen.  It's a pretty obvious idea and I know people are doing it, but I 
don't know what to buy.  Features I'd want:

4K video HDMI output (3840x2160).
8GB RAM
128 GB SSD
WiFi
Bluetooth
USB 3.x

It would be great if it were easy to install Ubuntu, say, and have 
everything just work.

I see that Beelink has some offerings that ship with both Windows and 
Linux installed.  I don't know which distro.

Anyway, I'm hoping that someone here has some experience with something 
and can point me in the right direction.  More power and features is 
always better, but so is a lower price!

Thanks in advance.

Mike