Note: some users are reporting they had to remove all PCIe cards sans their storage controller (SATA card) and GPU to install the firmware update. Mojave will not install if you have a non-metal supported GPU. Despite the annoyingness of having to meet the requirements, it was a necessary evil. Vulkan, the OpenGL successor, wasn't quite ready for primetime when Apple originally created Metal for iOS and thus decided to port it macOS. OpenGL has been a thorn in Apple's side for quite some time, as it's been nearly dead for years.
The biggest change for macOS Mojave is the deprecation of OpenGL and OpenCL.
