Don’t know what webserver is used.
You can put an NginX reverse proxy before the HTTP web site, but this doesn’t encrypt the backup data itself.
I do think I saw somewhere that that data is encrypted by the client before sending it over the backup port.
But I would like to be able to put the backup data stream also behind an NginX reverse proxy (on port 443). That way it wouldn’t be blocked by firewalls at my clients.