I was able to configure an IPv6 SDN subnet in PVE 8.3.2 via the WebUI.
Zone
IPAM
pve
automatic DHCP
true
Subnet
Set "DHCP ranges"
VMs get IPv4/IPv6 addresses via DHCPv4/v6.
Routing is next ;-)
Same problem here. The Fritz!Box 7530AX delegates a /57-prefix out of a dynamic /56-prefix delegated by the ISP.
How to forward the /57-delegation to a SDN-subnet including firewall rules and IPsets?