Don’t waste your time with Apple, they won’t respond. I tried getting a response for nearly two months on this matter and nothing… Unofficial feedback I’ve had is that AMD Radeon 6700 XT won’t be supported on macOS. The 6000 series cards that are currently supported all have an equivalent professional card ie AMD Radeon 6600 XT has equivalent AMD Radeon Pro W6600. The 6700 XT is the only graphics card that does not have a Pro version. I doubt very much Apple will go out of their way to produce driver/kext support, when all their energy is focused on development for their in-house chips.