I recently bought a Samsung 55" 4k smart TV and had no trouble setting it up with my old SA8300HD PVR. It came up as unknown because the old boxes are not in the database, but I renamed it afterwards.
just buy a LG c 7 55" 4 k TV
and how to set it up with net box explorer 8642HD?
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There's no setup required....just connect the box to the TV and it will work.
IF you want access to the 4K channels, however, you need a 4K box. The 8642 is not capable of displaying 4K content (its barely capable of HD content, but that's a topic for another thread).