I'm not sure if you can turn off HDR, check the manuals and online. I would also double check your player and your hdmi cable in case it's those causing the flickering.
I hope you're not actually clueless as to what HDR is because it's silly to buy such a TV without knowing. Either way, when a signal or video is HDR, it is normal to get a brief disruption because the TV is switching modes. I get it all the time on youtube and netflix. Basically, do your research, but for this kind of money, you WANT the HDR on.