Comment by simoncion

You're aware of DHCPv6 Prefix Delegation? The two US-based ISPs I've used in the past ~twenty years (Comcast and Monkeybrains) use it to provide IPv6 service and permit your DHCPv6 client to request a /60 prefix to use as you see fit. It's not a /56, but it's also very much not a /64.

I'd expect "Give home users a /60 via DHCPv6-PD" to be considered "best current practice" in the ISP "community"... so if I switched to another ISP that claimed to provide IPv6 addresses, "ask for a PD-assigned /60" would be the first thing I'd try.