We do backwards and forwards compatibility between v4 and v6 using NAT64+DNS64 between IPv6 -> IPv4[1] and a reverse proxy (delorean) for IPv4 -> IPv6 [2]. To ensure reachability to IPv4 endpoints without a domain, we use visibleip.com [3].
For our users, it doesn't matter if it's IPv4 or IPv6 - they can reach it, and it can reach them.
[1] https://blog.ipv6.rs/ipv4-activated-via-nat64/