Not allowed to install Big Sur to, boot from, external drive?

I'm trying to install Big Sur on a separate, bootable drive. I did a google search and was told to format my external drive (USB3 SSD) with GUID partition. macOS installer recognized it as a drive to install on but then during the install process, after the required reboot, I received an error message saying that security settings do not allow a boot from an external drive.

Any suggestions?
Hello, Flo, Did you format your external SSD with Apple's most modern file system (which, if I am not mistaken, should be AFPS)?

Kind regards ;-)
With the lastest version of macOS Big Sur, 11.0.1, they just made this possible. To create a bootable external hard drive / clone with Big Sur, I used the most recent version of CCC, 5.1.23 beta, and was able to clone and boot from the external drive successfully.
LKQuestions, did you managed to perform a full update post 11.0.1 to 11.1 on your external drive with that method?
Not allowed to install Big Sur to, boot from, external drive?
 
 
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