How does nextcloud use dhcpv6 to obtain an IPV6 address

I use nextcloud in unraid’s docker (unraid is a nas system). At present, nextcloud can obtain an IPV6 address through SLAAC, but I hope to obtain an IPV6 address through DHCPv6, because using DHCPv6, DUID can be used as DDNS on the router, which is convenient to use .