This is good advice. I kept my 4k Vizio offline until updating the firmware on a whim. The update broke the ability to run 1080p@60hz from my PC, making it effectively useless for normal use. The annoying part about the panel is that it was advertised as 4k but only works at 30hz at that resolution. Cheap, so should have figured.
Not a TV, but my monitor is 3440x1440. However, it only supports 30Hz at that resolution over HDMI since it has an older HDMI version. It only supports 3440x1400 at 60Hz over DisplayPort.
So, if your TV has any other inputs, might want to try those too.