DHCPv6 IA_PD - how-to

tl;dr; anyone have a good IPv6 network setup based on an IA_PD from
their provider?  Any details or advice to share?

The current router is x86_64 FreeBSD 11.x, but I’m building the FreeBSD
14.1 system to replace it now.  What to install on it for this is a pending
question.

Hello all.  I have been running a FreeBSD router for years and years.  I have
this year been trying to figure out how to use an IPv6 allocation from my
provider (Verizon FiOS).  They are using the PD feature of DHCPv6 to give
a delegation, and not given an address (NA) when asked.

There are, unfortunately, _many_ programs that can help me with this,
and google yielded no clear best-path.  I have not been able to get
ISC dhclient to work for me so far, and I did get dhcpcd working, but
only with command-line options rather than config file, and that
application doesn’t have the smarts to configure things based on 
the PD, so I’d have to code all of that myself.

Thank you.

                    - Chris