iptables?

Of course it's technically possible, it's all just packets of data that you can change, at the end of the day. I just meant that the easy way to do it (AIUI) went away with IPv6 because you were never supposed to need to do that, and with v6 you 'don't'.

It's not like the purpose of firewalls is redirection.

I thought that iptables was the easy way to do it? (Both for IPv4 and IPv6.)

NAT66 is an experimental (10 years old IIUC!) RFC for one-to-one IPv6 mapping. While there's no RFC specifying an official method of masquerading behind a single address, AFAIK iptables "just works" (as long as you aren't running FreeBSD).

Create a loopback interface and assign it the IP address you want redirected, then have your DNS resolver bind to those IP's.