Please clarify how to install OpenCore

[night nova]

I have a MacPro 4.1 flashed to 5.1 with a non-flashed RX 580 GPU, which used to work with Mojave, but installing OpenCore resulted in Prohibition sign at start, and I've lost the Recovery partition as well, no idea how it happened, so I'm doing it again from start. I created an USB flash with a Mojave install on my other MacBook Pro 16, selected a "MacPro 5,1" preset in the Settings, "Built&Install OpenCore", select the USB flash and the EFI partition as target, it completed successfully. If I boot the MacPro with the USB flash, I can see the OpenCore "EFI boot" icon, but selecting it results in a black screen for a few minutes, then an automatic restart.

This note from the docs is not very clear:

"For Mac Pro, Xserve and, iMac users with non-flashed GPUs, you can still easily boot OpenCore and view the entire boot process.

Firstly, open the Terminal and run the following command:

How do I do that, considering I still have an unbootable system ? Thanks for any help.

[jolly gull]

The reason you're getting the prohibited symbol is because OpenCore is spoofing the Mac Pro 5,1 to a model too new to run Mojave (the 2019 Mac Pro). You'll have to change this for it to boot.

[jolly gull]

Oh wait, you're saying you are able to get a boot picker from your USB flash? If so, this is already an OpenCore boot menu - do not select EFI Boot from here, select your OS option

[night nova]

Hi, I managed to install Monterey, and it worked fine.

Worked fine, until I tried to add a driver for a flashed Titan Ridge 2.0 Thunderbolt card that came with an USB stick, it's a file named SSDT-TBOLT3.aml, which worked when I was running Mojave (before the mess up), the stick came with an older version of opencore (sept. 2021) and with Cloverconfigurator.app so, I didn't used it and, instead, used the latest OpenCoreConfigurator.app, mounted the EFI partition on the Monterey SSD which worked fine even without the USB stick, opened the existing Config.plist with the Configurator, added the SSDT-TBOLT3.aml to the ACPI drivers, noticed it did changed the Config.plist, so I saved it back, unmounted the EFI, reboot, now I get a black screen and cannot even start from SAME USB Flash I used before to install Monterey!!

[jolly gull]

OC Configurator is known to sometimes screw up the syntax of the config.plist file. you're better off using a text editor

[night nova]

fair enough but, how's that my USB flash drive, the same that I just used to install OC and Monterey, now doesn't boot anymore ? I tried "Build and Install Open Core" again on the stick (on another Mac, using MacPro 5.1 settings), even with the Debug version and the Verbose option, and nothing, even when restarting pressing the ALT key ( I'm using a Windows keyboard ), I can see the Mac is accessing the flash drive, because it has an access led, but after a few seconds, it stops and stays there on a black screen.