Thanks. I've tried SingleFile. I made some backups using the Chrome Extension. I was unable to open them a couple of years later. So I abandoned it.
Will try karakeep.
Will try karakeep.
Edit: What's the best way to support the project? I'm seeing there's an option through the Mozilla store and through GitHub. Is there's a preference?
I would look into what happened with the single file copies you made that didn't work because that is highly unusual.