It you directly update the DDNS servers from your router it will only add the IPv6 address of your router and NOT the IPv6 of your devices since they get their own unique IPv6 addresses. It is a very bad idea to expose your router on the Internet since it will be under constant attack.
@openwrtforever That has nothing to do with the inability to add IPv6 DDNS service with Joker.com as can be done with afraid.org. Since the router IS on the Internet, it is under constant attack anyway. Having a DNS entry that points to the router does NOTHING to change that.