In my #proxmox #sdn experiments, I've noticed that after adding the IPv6 subnet to the vnet, applying the config, and then changing an existing lxc (and doing a power cycle) it does get an ipv6 address in the IPAM view, but it does not get added to /etc/dnsmasq.d/<zone>/ethers.

Hence, it doesn't work until you add it and apply SDN again.

Smells like a bug to me.