I've been using SuperDuper for 7 years without issue and have recommended it to others. I don't blame the developer for this issue, which arose from a change in macOS, but I'm pretty disappointed in their response.
The worse part of this issue is that SuperDuper completes the cloning process and does not notify the user that the cloning process failed. To make this worse, the front page of the SuperDuper site contains the following:
"v3.3.1 now available! The latest version of SuperDuper! is faster, better, fully compatible with macOS Catalina (10.15)"
There is a workaround, which involves using the Apple Software Restore (ASR) utility to create the initial copy, after which SuperDuper can be used to do smart updates. However, you have to email the developer to learn about this workaround.