Powering off during startup questions.

If you can boot up on an external bootable drive. Restart the system with the external connected and press the Option (⌥) key to enter into the Startup Manager to select the external drive. Did that work?

Reference: Mac startup key combinations

If it did then the SSD drive is messed up which would not surprise me! Super Duper can’t setup the APFS structures properly. You’ll need to reformat the drive fully, re-install the OS either via a local OS installer or Internet recovery. Then lastly, use Migration assistant to move your old drives user accounts, apps and data to the new drive.

I haven’t used any cloning app for a good 10 years now due to the fact cloning doesn’t deal with file errors or drive structures like you encountered here. Even when it appears to work you can encounter app and data issues where the file is missing parts corrupted where a copy with CRC would either find the missing piece or alert you the file was too badly damaged, cloning apps won’t do that!