ISP IPv6 Subnet delegation pass-through

[Ed V.]

Related to: Feature Requst: KEA DHCPv6 "shared subnets"

As an alternative to official "shared subnets" support, is there a way to "pass-through" the IPv6 subnet delegation from my ISP (Cox Cable) to a standalone Kea DHCP server?

The Kea "readthedocs" site infers that such is possible, but doesn't give any specifics or details - saying it's up to the "router vendor".

I did some keyword searching in the OpnSense docs along with "Dr. Google", but nothing useful turned up other than some confusion regarding PD pools and subrouters (none of which was very clear - most posts said something like "after I played around with it for a while..." but gave no details).

Any thoughts, help, links to good docs, etc.?