How can I override a domain with local LAN ipv6 address with unbound?

[heypppoe]

HAproxy running on the opnsense box with a dedicate domain + SSL, how can I add a override in unbound and assign the LAN ipv6 address to it? (LAN ipv6 address come from track WAN interface, will change every week).
I have dhcpv6 running and RA set to managed, DNS v6 server set to unbound by default.

[Maurice]

So this is meant for internal access only? Then I'd add a ULA IP alias to the interface and put that address into Unbound.

Cheers
Maurice