Struggling to wrap my head around Docker and IPv6

I am struggling to get IPv6 up and running in my Docker containers. Through a combination of reading this documentation, this documentation and on the surface it seems to be running, if I do

docker run -it alpine ash -c "ip -6 addr show dev eth0; ip -6 route show"

as mentioned in the first documentation page I linked I get:

92: eth0@if93: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1500 state UP 
    inet6 2001:470:<censored>::/64 scope global flags 02 
       valid_lft forever preferred_lft forever
    inet6 fe80::42:acff:fe11:a/64 scope link tentative 
       valid_lft forever preferred_lft forever
2001:470:<censored>::/64 dev eth0  metric 256 
fe80::/64 dev eth0  metric 256 
default via 2001:470:<censored>::1 dev eth0  metric 1024 
ff00::/8 dev eth0  metric 256 

Which means I have IPv6 addresses in my containers right? Well no. I still can’t access any containers via IPv6 and when do curl -s in any of my containers I never get any output, whereas curl -s shows my public IPv4 address as expected.

This is what I have in a Systemd dropin as trying to add this to the docker.json file causes Docker to fail to start:

ExecStart=/usr/bin/dockerd --ipv6 --fixed-cidr-v6 "2001:470:<censored>::/64"

and I also ran sysctl net.ipv6.conf.eth0.accept_ra=2. The IPv6 settings on my router show this: postimg,cc/mt2zQ3kq So am I entering the wrong value for fixed-cidr-v6 or is there something I am not doing?