> Unfortunately, disabling uPnP these days is too much of a hit to convenience, so I looked for other solutions. Don't do this, there is no good reason to run UPNP if you care about security, turn it off and learn to manage a firewall. If the author really cares, go one step further and replace the ISP owned router with something with more control. Finally, if one cares about the software one's NAS runs, build or buy…
I find it amusing that many people are convinced that IPv6 is less safe, because there is no NAT, and at the same time use UPnP. No, NAT isn't designed for security, the blocking of incoming traffic is just side effect, you should use a firewall for security.
The issues with IPv6, in my experience come from its relative complexity, compared to IPv4, and also from forgetting to manage it at all, as it often uses different tools, firewalls, e.g. ip6tables vs iptables, or the fact that Ubiquiti EdgeRouters don't expose ANY IPv6 firewall configuration in the GUI at all.