Hi Maverick, check these instructions and adapt them to your BIOS.
Than use Still_waiting_for_root_device.zip from my upload-folder, possibly it may help
i did try once more time when use USBLegacyOff=Yes this flag i got stuck in
AppleNforceAta found0 Unit but capsLock is still work but won't get further
i use this flags
-legacy -v GraphicsEnabler=Yes USBLegacyOff=Yes -x -f
-legacy UseKernelCache=No USBLegacyOff=Yes -v -f -x
i am using brozowaka amd kernel v4 and v5