While troubleshooting my private IPv6 connectivity, I decided to enable an IPv6 and IPv4 specific access to the forum, so you and everybody else can test it:
https://ipv4.vulndetect.org/
https://ipv6.vulndetect.org/
https://vulndetect.org/ is naturally dual-stack and most of us need not worry, once you have IPv6, you will use it automatically (if your ISP set it up correctly).
It appears that my ISP currently has a routing issue, but then I could use my cellphone (just needed to enable dual-stack support in the APN under Mobile network).
We also expect to enable dual-stack access to the VulnDetect backend, at some point during the tech preview stage.