Hi All,
Thank you for your responses. I went back and ran CCC and selected the option for Legacy Bootable Backup Assistant. Just as it was finishing I saw a message that "cloning failed" and then CCC finished with a "Successful Backup" message. I shut down and then restarted and held the power button to bring up the startup options. It launched right into Startup Disk, which I closed. I restarted again and held the power button to get the startup options and there was an icon for my external drive. I selected it and was able to boot from the external drive.
Overall, the behavior of creating the bootable external drive and then booting from it seemed sketchy, so after I had shut down and restarted on the internal volume, I erased the external drive and then did a standard Backup with CCC. Since the CCC web page from the link in one of the above posts said that if the internal SSD of a M1 Mac fails, the machine cannot boot at all, even from an external drive, there does not seem to me to be any point in trying to put up with the quirkiness of the M1 machine and trying to create and use a bootable external drive.