Documenting settings to get IPv6 setup within the configuration for OpenVPN, plus forwarding all IPv6 traffic through the VPN. This has no explanation of how you obtain IPv6 address prefixes frrom your ISP or how it works differently from IPv4, just simply how to get it working within OpenVPN. Will update if needed.
I’m archiving this information for future reference because I (or others) may need it. This was extremely helpful in getting AT&T’s allotted IPv6 subnet(?) (properly called: delegated prefix) setup in my EdgeRouter 4, although I wound up having to use the web interface and configuring the same settings within the Config section. Without further ado (or a whole lot of ado below) here is Bradley Heilbrun’s explanation.