Dave Nanian, writing about SuperDuper! on Big Sur:
At present, it’s not possible to make bootable copies of Big Sur, even with
asr, Apple’s own built-in replication utility. As such, we haven’t released a Beta, or even an internal Alpha, because it wouldn’t meet our own requirements.
So, for the moment, we’re holding back, hoping that Apple will fix the issues and allow 3rd party (or even 1st party, given
asr) bootable backups. While
asrwas failing completely in previous builds, in the most recent one it isn’t able to back up because the system volume isn’t properly ‘sealed’ (which is ominous, since why wouldn’t a standard install be sealed, and if it’s not, why wouldn’t you be able to back it up anyway).
So, while progress is being made, we’re kind of stuck waiting for the king.
This is from about a month ago at this point, but I haven’t seen any new information that shows bootable backups are possible with newer betas.
Over the past few years I’ve been much more hesitant to upgrade macOS immediately after major version are released. My machine is far too essential to risk breaking anything. So I’ve been waiting several months before I upgrade.
Even if that wasn’t the case, though, this news about the inability to create bootable backups would give me pause. Although, Time Machine and Backblaze are my primary, everyday backup systems, SuperDuper! is essential to me. When I travel or send in my machine for repair, albeit rare, I always do a SuperDuper! backup so I can get up and running quickly if anything happens.
If I upgrade to Big Sur and bootable backups aren’t even possible, I’d always have a little bit of worry in the back of my mind that I would want or need to create one and wouldn’t be able to.