After installing pihole (but not right after which made troubleshooting challenging, it took about a week to demonstrate the problem) my android device, a pixel 5, began constantly disconnecting from wifi. I finally narrowed it down to pihole on IPv6. Using public dns for IPv6 and pihole for IPv4 everything worked fine and the phone connected. As soon as I set dhcp to use pihole for IPv6, the phone started disonnecting again. I could not find any blocked queries from my phone at all, let alone something that would indicate a connectivity test was being blocked.
My pihole installation is 100% standard with some public adlists installed and a very small collection of blocked domains in a local file, none of which have anything to do with google or android.
I'm stumped and curious if this has been seen before....my keyword fu may not be great because I found nothing when searching the forum.