IPV6 on Unifi Dream Router - IPv4 DNS sneaking through

I've switched from Google Wifi to Unifi Dream Router and am trying to use NextDNS with IPv6 to replicate the family group features - where different endpoints get different DNS info.

Unfortunately, router requires me to enter an IPv4 DNS server even though it has IPv6 DNS options that work. On windows machines this results in the IPv4 DNS being added and prioritized above the IPv6 DNS (It also resolves the IPV4 DNS to an equivalent IPv6 DNS).

Is there a way of setting things up so I get DNS by IPv6?