Thanks for the details.
In my experience, very exasperating for sure, my self-signed certificates were not properly configured on the source and destination sites.
I’m not making any assumptions about your use case but this site may be helpful in verifying everything is set up correctly: Link:
You might also try setting up a source and a destination test site in a localhost environment. Lot’s of people use Flywheel Local because it’s “free” but it may in your experience, (like it was in mine), be a pain in the a** to configure for self signed SSL certificates.
Not to tell you how to develop, but in my workflow, I develop a site locally first and then use All In One Migration to transfer my work up to the live server. My personal preferred localhost is MAMP which has a Windows version now.
For a live hosted service I used InMotion Hosting with a vps and their self signed certificates are working as expected for cross domain copying using Bricks Builder for me.
Lastly, be sure to use your Chrome debugger to verify if the copy to the clipboard is functioning as expected.