I've got to echo what poquest33 and CrockD have said, being asked to swap cables or alter a TV's functionality for a single game is asking a bit much. I do understand that you want to eliminate every possible angle in hopes of finding a solution and I would be willing to help test your suggestion for that reason. Sadly, I don't have an old HDMI cable and as far as I can tell my LG TV doesn't have a setting that would allow me to change an HDMI port to 1.4 like that reddit user's TV.
I can and have tried disabling wide color gamut/HDR as previously suggested and have tried the other ports on the TV to see if the one my PC is connected to was somehow faulty and that didn't solve the issue either.
Also as others have said, this is the only game I have the problem with. If this were an issue with even one other game then I would think my TV or even my Nvidia card were in need of an update or a possible repair/replacement. I am curious about what CrockD said and perhaps it is the pairing of an Nvidia GPU with an LG TV causing this. It would be great to hear if someone using an AMD card has the same purple or black screen.