As I've said before. The server behind the router does not have a public IPv6 address. It is NATed to the Internet. Getting the internal IPv6 address is useless for this case.

I do not like to have the servers/computers that are on the internal home network directly connected to the Internet.

Nating in the context of ipv6 is not a common thing. It is the exception, while it's the rule for ipv4