Installing Sierra 10.12 to Big Sur External Drive - "This version cannot be installed on this computer."
I'm running Big Sur 11.0.1 on a 2019 iMac trying to install Sierra on an external Drive. I formatted the drive APFS, downloaded the installer from Apple but when the package is executed, a message indicating "a program will be run to determine if the software can be installed." Ok, run that then "This version cannot be installed on this computer." I don't want to install it on this computer, I'm installing on an external drive. How do I get past this?