IPv6 Discussions
I believe they do it the same way they do to others because fundamentally the IP stack is not considered in the search algorithm. Results should show up, if the user doesn't have IPv6 oh well user's problem.
There's always this guy from Google saying the same: https://www.seroundtable.com/dual-stack-ipv4-6-google-seo-30152.html
This guy is talking about dual-stack, and I was talking on IPV6 only, when your site is unavailable for someone that doesn't have an IPV6 connection
Same thing for the search engine. The search engine doesn't care, it serves full urls based on domain names, not IP addresses thus it is up to the user to have IPv6 or not. What I do know is that their bot seems to pick/prefer IPv6 to index a website if the website has it, I believe the bot isn't probably even aware of what IP stack it's using - like any other program it does DNS resolution, gets whatever IP is available and fetches the website.
If a site is ipv6 only then its DNS will only have AAAA records. When an ipv4 client tries to visit the site it will request an A record, which won’t exist. So the browser will just show an error that the site can’t be found.