When I run fly dig with my dbname, it gives back the expected IPv6 address.
One quirk is I can’t get into any of the images that exhibit the problem.
fly ssh console
Connecting to <address>... complete
Error error connecting to SSH server: ssh: handshake failed: ssh: unable to authenticate, attempted methods [none publickey], no supported methods remain
When I use fly ssh console -v and pick my older instance, I can get into it. When I run dig top2.nearest.of.<dbname>.internal from that instance, it gives back the expected address.