I use dual-stack for client and server with observium.
By default browser use IPv6 (it is great).
All in observium is works for me.
But I have too many logouts with message "Remote IP has changed" when I use SLAAC with Privacy Extension on my computer.
My IPv6 address changes every X hours, so I need to relogin from every IPv6 address.
I suggest to allow changing IPv6 address for user if it is the same /64 network.