Cannot Update System Definition from 14,2

Hey all,

I'm currently on Mojave, prepping to update to Big Sur. Got all my ducks in a row in terms of updating firmware, patching ACPI after firmware update, and making sure all my apps are 64bit compatible. Now the hard part.

I have tried multiple system definitions from iMac Pro 1,1 to iMac 18,1 18,2 18,3 19,1 19,2. All of these clear the verbose boot stage but then the monitor shuts off as if its no longer getting a signal from the GPU (AMD RX580). If I go back to 14,2 then everything...

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Author: Krow01