This shouldn't affect most users.

AMD has announced that its upcoming RX 9070 series (RDNA 4) GPUs will require a UEFI system for optimal compatibility. Put simply, it has dropped support for the older BIOS and CSM standards, requiring users to make the necessary shift to UEFI. While this doesn’t mean RDNA 4 GPUs will cease to function with legacy firmware, AMD offers no assurance.