No DNS resolving with use of de IPv6 LLA of the server

[deHakkelaar]

@bert_krale

Resolving a domain name via the ULA (fe80::<redacted>02)

Not related to the issue but above IP is not a ULA but an LLA with that fe80 prefix:

IPv6 Fundamentals: A Straightforward Approach to Understanding IPv6, 2nd Edition

ULA's have a fc00::/7 prefix (from above diagram).
See also below:

Use IPv6 ULA addresses for Pi-hole

Many users have reported that frequently changing IPv6 addresses cause page load to be slow or even prevent from working at all. The issues can be fixed by updating the IPv6 address in /etc/pihole/setupVars.conf followed by a run of pihole -g. However, this solution turns out to be very inconvenient since it might be necessary to change the IPv6 address on a regular basis (maybe even multiple times a day). An alternative approach we are currently looking into is the usage of ULA addresses which…