Failing while installing macOS, is a sure signal of NVRAM volume problems, even more so if is failing while in the grey screen. Major cause of failure to install macOS back in Big Sur times.
Also, frequent KPs are a major cause of bricks, since the crash dump is saved inside the VSS store and can easily corrupt the NVRAM volume with MacPros before the MacPro7,1.
Code:
sudo nvram boot-args=“-v”
If you want to do a kernel messages/debug step by step, no it's not possible (unless remote debugging with a very complex procedure and requiring specialized hardware).
If what you want is to force the startup Manager to appear every boot, only works for GPUs that have pre-boot configuration support:
Code:
sudo nvram manufacturing-enter-picker=true