Not sure how do I do that? .
Under Advanced IPV6 if I disable Connection Type then all IP6 traffic is blocked and I https://test-ipv6.com reports :
No IPv6 address detected
When a publisher offers both IPv4 and IPv6, your browser appears to be happy to take the IPv4 site without delay.
Connections to IPv6-only sites are timing out. Any web site that is IPv6 only, will appear to be down to you.