IPv6 internally IPv4 externally?

Does anyone assign IPv6 addresses on their lan but only connect to the internet via IPv4?

Any use of something like NAT64? Is this possible on the Omnia?

Knot-resolver has dns64 module that should do the DNS part, if you configure it.

The IP part – I guess the “firewall” might be able to do it, but better take advice from others on this.