In my case I run a double NAT. I don't consider the subnet which the ISP's router offers to me as something belonging to me, but something the ISP owns. In that subnet I have one honeypot (old Raspi) and a router which treats that subnet as the internet and offers me my own subnet which I call home.

I don't care what the ISP does with the router it provides to me. If it uses IPv6 or whatever. In my case their router will only see another device which is only capable of using IPv4, so it better deal with it.