clone os to ext hd make bootable

Keep in mind making bootable clones of M1/M2 Apple Silicon Macs may no longer work properly. The developer of CCC mentioned that bootable clones for macOS 11.x+ is on a "best attempt" basis and is no longer guaranteed to work. So far, I have not had any problems on Intel Macs, but last year I saw numerous posts on these forums where macOS 12.5.1+ clones were no longer possible on Apple Silicon Macs (some seemed legitimate).

I suggest you begin to look at other options than bootable clones.

Here is the information provided by Michael Bombich, the developer of CCC (further down this article is the now recommended way of having a spare boot drive with your data if a bootable clone fails):

https://bombich.com/kb/ccc6/cloning-macos-system-volumes-apple-software-restore

I'm sure that SuperDuper has the same limitations and will require similar methods as well, it is just that the CCC developer really communicates well about these issues.

Do not use Super Duper but the another cloning software Carbon Copy Cloner

Would suggest reading from link below

https://bombich.com/kb/ccc6/macos-big-sur-known-issues

Cloning involves using the ASR Feature built into the Operating System and is required to be used by these cloning softwares Developers

Of Super Duper or Carbon Copy Cloner application do not fit your requirements or does not work >>>

This article form a respected Contributor to the Forums has a How to Article that is very detailed on using the ASR function

Not for non-Tech Savvy users

How To Clone Your Mac Using ASR

Ah, semi false error message and rather misleading.

From my experience.

The Bootable Installer of High Sierra was made a long time ago and needs to recreated with a More Recent download / creation of the Bootable Installer.

It is possible the Apple Certificate contained within the Installer that was downloaded has Expired.

This was and remains a similar issue for the OS X 10.12 Sierra that Apple is aware of but never fixed.

Very Welcome.

Do keep us posted on the progress, if time allows.

Should additional questions arise, do ask in a reply posting

Disregard as a Double Posting