Some mobile networks are IPv6 first, and only have IPv4 through NAT64 and similar mechanisms. At times, those may be capacity limited, and v4 service can get pretty iffy. (Many moons ago, I experienced an ISP with a less than second inactivity timeout on TCP connections to our servers; that was lots of fun, but seemed to be an issue on their NAT64 gateway, and wouldn't have been an issue on v6).<p>You're also likely to see a lot more IP sharing between users on v4 than v6.
There was one reddit thread with a person saying that his ISP was IPv6 only and only dual stacked sites loaded for him.
apparently it was small rural US ISP, but the user did not gave more info.
Not as far as I know. I doubt anyone would care about my hobby sites but my last work-place was used by thousands of businesses and we only used ipv4 on the load balancers and CDN endpoints. No issues, no customer complaints. AFAIK no customers asked for ipv6. If anything we had to support really old ciphers and had to make special firewalled API vips for customers that needed things like SSLv3 until they could get their vendors to upgrade their client libraries.
My VPN solution is that I run Wireguard on a server with only IPv6 connectivity.<p>So when I am connected through that VPN I see some breakage, e.g. github and some CDNs not working.