DMUG #3: Important, before installing macOS Monterey 12 on a Mac Pro 5,1 2010...
Recent developments in the OpenCore regarding macOS 12: Monterey suggests you may want to hold off on upgrading. This is due to SecureBootModel (SBM). Enabling SBM will leave pre-macOS 11 Big Sur installs unbootable. Also, clearing your NVRAM appears to wipe out the SBM.
/edit: DarthRevanG4 on Reddit points out adding -no-compat-check to opencore can scoot around the issue of not being able to boot Mojave. See his post for details!
https://www.reddit.com/r/macpro/comme...
Also there is a work in progress fix:
https://forums.macrumors.com/threads/...
Second, Monterey 12.1 Beta 1 introduces more widespread use of RDRAND which leaves older Macs unbootable
OpenCore on the Mac Pro Warning
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OpenCore Legacy Patcher - Issue
https://github.com/dortania/OpenCore-...
Mac Sound Solutions Mac Pro 5,1 Opencore Mac OS Monterey install
• Mac Pro 5,1 Opencore Mac OS Monterey ...
https://forums.macrumors.com/threads/...