Hey @user2FjKeHh8sj ,
It seems like you may have a string of LEDs that may either be out or dim. Due to the size of the screen you qualify for Samsung in-home service. Contacting the Customer Support number will get you a service date. Due to the COVID-19 pandemic there may be a delay. I hope this was helpful please leave a like and mark accept as solution if this answered your question.
Loads of Samsung TVs do this, it isnt isolated. I would definitely do some research and try and get it fixed for free as this is a hardware fault over a large percentage of TVs.
Oh, and obviously do not buy another Samsung TV.