I am using the 98 inch version in a dedicated ht dark room..To me PQ is better than LG C4 with higher contrast with similar black levels but you need to configure the right setting but I am not using antenna port as it is lightning prone..If you still want to use better use an external decoder box and connect via HDMI which is safer.
However c855 upscaling of non 4k source material while good for most people but is not as good as Sony, Samsung and LG TVs of similar tier.
If your viewing mainly non-4k broadcast sources, I will suggest either a Sony or Samsung which excels in upscaling.
For me it does not matter as I am using a high end video processor to upscale for non-4k source and most of my viewing are 4k sources.

Hi,

No problem. Please take note c855 is using high contrast VA panel. Unlike IPS panel it does not have very wide viewing angle (similar issues with Sony and Samsung miniLED VA panels which does not have wide angle filter)
Viewing directly in front is no issue for the picture quality.
But if you view at more extreme angle from sides, there will be color and brightness washout
Example main sofa in front of TV is ok  but if side sofa to the left or right at 90 degrees of main sofa, picture quality will degrade.

big retailers like Sengheng, Onking, not in the list?