IPv6 Examples

Hi. I just received this device today (60F) to replace some EdgeRouter products and I'm having a hard time getting IPv6 to work. So far, I was able to follow a guide here: https://thorsten-on-tech.blog/2018/06/08/ipv6-with-prefix-delegation-on-fortigate/ 

Setup;

WAN1 -> Comcast Business 

Port 1-2-3-4 (desktop devices)

Port 5 WiFi Router

Should I be using the 'internal' interface (ala switch0 on EdgeRouter products) or something else as a config example?

For example, when I do this I am getting IPv6 addresses from Comcast on the desktop devices et al, but IPv6 testing from external doesn't work.

config system interface
  edit "internal"
    config ipv6
      set ip6-mode delegated
      set ip6-allowaccess ping https ssh
      set ip6-send-adv enable
      set ip6-other-flag enable
      set ip6-upstream-interface "wan1"
      set ip6-subnet ::1/64
      config ip6-delegated-prefix-list
        edit 1
          set upstream-interface "wan1"
          set autonomous-flag enable
          set onlink-flag enable
          set subnet ::/64
          set rdnss-service default
        next
      end
    end
  next
end


config system dhcp6 server
  edit 1
    set dns-service default
    set subnet ::/64
    set interface "internal"
    set upstream-interface "wan1"
    set ip-mode delegated
  next
end