I am trying to install Mac OS Big Sur on an external drive (Samsung portable SSD T5 256GB) following the macworld directions. I get to the very last step, however there is a message that the disk is locked and it can't be selected, so can't install macOS on it.
I have previously installed macOS on the drive using restore from backup, but I just want a minimal OS install, not all my stuff from a backup.
I have also tried to select the drive as the boot disk, but get a message that I can't select the drive because "the bless tool was unable to set the current boot disk".
Any ideas on how to rectify this?