In the Graphics section where it says to use WhateverGreen, I think there should be a disclaimer saying that even when using an AMD iGPU and planning to use NootedRed, the installer does not support NootedRed and you should use WhateverGreen until you get MacOS installed and then change to NootedRed. I spent a lot of time and happened to find one tiny article that said that, and as soon as I swapped NootedRed with WhateverGreen my problem was fixed.
Opencore Install Guide https://dortania.github.io/OpenCore-Install-Guide/ktext.html#graphics
In the Graphics section where it says to use WhateverGreen, I think there should be a disclaimer saying that even when using an AMD iGPU and planning to use NootedRed, the installer does not support NootedRed and you should use WhateverGreen until you get MacOS installed and then change to NootedRed. I spent a lot of time and happened to find one tiny article that said that, and as soon as I swapped NootedRed with WhateverGreen my problem was fixed.