When I tried to download macOS Big Sur on an external usb, I could only get it to work by using GUID partition mapping and APFS unencrypted format, though you will need at least 35gb of free space to download it
I hope this works!
CodyBrooks
Users receive reputation points by contributing quality content to the forums.
Posts include post and replies published on the forums.
Post authors can mark replies as Accepted to indicate successful solutions.
Apple Developer Forums admins can mark replies as Apple Recommended to indicate an approved solution
User for
From
New South Wales, Australia