AdGuard with IPv6?

I am working on GL-AX1800 with FW v4.2.1r4.
My ISP provides IPv4 and IPv6.
On my Android 13 phone, I have installed Network Analyzer to check network information.
On “DNS Server IP” it shows my router IP (gateway IP).
On “DNS Server IPv6” it shows an IP address of my ISP.

I have tried changing: OpenWRT → LAN → DHCP Server → IPv6 Settings
DHCPv6 Service: Server Mode
Announced IPv6 DNS servers: [ddc0:f483:9c59::1]:3053
However, it does not accept [ddc0:f483:9c59::1]:3053 or ddc0:f483:9c59::1#3053

How to make DNS IPv6 to be router IP?