They have been claiming that IPv6 is the future for 20 years and it still is not fully supported by even the very largest ISP.
In a lot of cases it performs much worse. Hard to say exactly why but I know a lot of times the latency to sites is much higher because the data follow a longer path. Even when it function the way it suppose to you will get less total through put purely because the length of the headers in IPv6 eat up more of the data packets.
There are only a very tiny number of sites that run only on IPv6.
The biggest issue for me is the abuse by all the large internet companies. If you use IPv6 it allows them to track all the way down to individual device because it contains the mac address and other unique identifiers.
In any case you only option is some kind of VPN. If you can find sites that support teredo tunnels that will work but in most cases it serves no purpose. You are going to the site via IPv4 and you have just added the overhead of IPv6 inside the packets. I know there are actual VPN companies that use encrypted IPV4 tunnels and the allow both IPv6 and ipv4 to pass through.
I am not sure it is worth the effort. I tell people all the time here to disable the IPv6 support to try to solve problems. You will at times get very strange performance when some of your data is running IPv4 and other IPv6