IPv6 prefix not routing
Like others, I'm having trouble with IPv6 routing - no matter how I set it up, I can't get subnets within my /56 (or the lower /59) to route into my router. DHCPv6-PD does work, in the sense that once a prefix is assigned, it gets routed, but other addresses within my /56 or /59 do not route, and the only thing my router gets for attempts to reach those is a anycast neighbor solicitation multicast message. Since the PD prefixes change randomly over the time even with a fixed DUID, I'd like instead to manage my own prefixes within the broader prefix that Comcast assigns me, and just get the whole /56 or /59 routed to my own router (i.e. have it set as next hop).
What I'm seeing seems very similar to this other post, notably point (1):
How can I do this?