I saw this suggested in another thread but that thread was locked so I'd like to propose this here.  Having multiple IP addresses is one of the touted features of IPv6, but also of note is that due to privacy concerns IP addresses are expected to change frequently with IPv6.  This makes setting up a LAN DNS server for IPv6 quite difficult since there is no reliable stable IP address to use other than the link local one.  Perhaps the way to accomplish this would be to add, in wired network -> LAN settings, a section to set up a unique local address prefix in addition to the SLAAC or whatever global address acquisition method is already set up.  It could be quite similar to the "manual prefix" setting that is there now, but be validated against fd00::/8 or fc00::/7 instead of the 2000::/3 that is there now.