Thanks. Honestly I don’t know where the example.com came from. Since the installation script discourse-setup doesn’t work for this use case, all that I did was to edit containers/app.yml and then do a launcher rebuild app. I guess this missed overwriting an example.com somewhere.
But anyway, I still managed to fix my setup. Rather than bootstrapping a fresh installation and restoring my backup, I created a tarball of the entire /var/discourse directory from my original server, did a rebuild over the top of that, and voila… everything seems to be working fine. So that’s the way that I’ll restore a backup in future. 