Use a tool like EFI Mounter v3 to manually mount the EFI partition of your destination drive before running MultiBeast.
Apple’s installer often creates a 200MB EFI partition. This is too small for HFS+ bootloaders. You need 300MB minimum. multibeast high sierra installation failed
Troubleshooting MultiBeast: What to Do When Your High Sierra Installation Fails Use a tool like EFI Mounter v3 to
sudo mkdir -p /usr/local sudo chflags norestricted /usr/local multibeast high sierra installation failed