Under his videos are the links to download the opencore package it’s just a small.zip file. The first video of his which is in the middle of the page so scroll down some, shows you how to install his opencore package it takes less than a minute once you review the video and do it, it’s very fast. Reboot into your system and download Martin Lo’s opencore package for 5,1, this link below.
Next boot into recovery mode and turn off SIP. Make a clone backup of your system just in case. You need to have Mojave installed because it installs a new firmware for the 5,1 or you can run the Mojave installer and stop after the firmware update. Here is a quick over view links are also in my video description.
PCIe strange is the main issue and it may get fixed it maybe this is the end of the road. Now that Apple updated to 11.3 via software updates you will have to get the older Big Sur installer for 11.2.3. Important note: Mac Pro 5,1 is not compatible with Big Sur 11.3 only 11.2.3 with opencore.
