Hello,
I have tested in a dev environment to upgrade from 5.10 to 5.12 and also to 6.0.0.2, but in both cases the IPv6 addresses are missing from the dashboard. It is also not possible to search for VMs by IPv6 address anymore.
Is this a known bug?
There has been some work on improving how IPs are shown in Sunstone. IPv6 should be there. Could this be a cache issue? Could you try in an incognito window or clear browser cache?