How to override (or a least view) the RDNSS ipv6 DNS? (root)

As far as ipv4 DNS is concerned, Android (at least version 9) can override default DNS settings fairly well. Firstly, it is possible to set net.dns* to the desired value. Secondly,

-t nat

works, and lets the user redirect the packets to port 53 anywhere required. With ipv6 however, things are not that easy. Android 9 (at least mine) does not support

-t nat

. Moreover, Android sets some internal DNS-related setting when obtaining the DNS address from SLAAC/RDNSS, which is not reflected in

, and insists on using it, regardless of what is in net.dns*. The only tool I am aware of, that might be somehow useful, is

-t mangle

, but it still seems quite limited. How can I override (or at least view) the default DNS address obtained from RDNSS?