You are already using Pi-Hole as DHCP. There are a few things you can do.
On the client from which you showed the ipconfig, go to the IPv6 setting for that network interface and disable it.
On your Pi-Hole, tidy up the IPv6 addresses. From your debug log, you have multiple IPv6 addresses, but none match what Pi-Hole is configured to use:
[✓] IPv6 address(es) bound to the eth0 interface:
2001:1c04:2404:1000:f31:b391:b60c:7b20 does not match the IP found in /etc/pihole/setupVars.conf (https://discourse.pi-hole.net/t/use-ipv6-ula-addresses-for-pi-hole/2127)
fe80::925a:3409:9fa8:e484 does not match the IP found in /etc/pihole/setupVars.conf (https://discourse.pi-hole.net/t/use-ipv6-ula-addresses-for-pi-hole/2127)
IPV6_ADDRESS=2001:1c04:2404:1000:f53d:cfe2:bb2f:a097