This just isn't how dual stacks that are only able to obtain an IPv4 address work. For DNS, if your device decides to perform a AAAA lookup (despite not having

This just isn't how dual stacks that are only able to obtain an IPv4 address work. For DNS, if your device decides to perform a AAAA lookup (despite not having an IPv6 address), it would succeed just fine, even over an IPv4 connection. (You can query any record type over the DNS connection/protocol, regardless.) If your device attempted to connect to the resulting address (I don't think most would, but let's assume) it would instantly fail, as there wouldn't be a route to that destination, and fall back to the next record — the A/IPv4 record. There are literally millions of dual stack laptops, phones, tablets, etc. all out there on backwater residential ISP networks that have no idea what IPv6 is. If dual stack didn't work — it'd be a real bug that would have long since been fixed. Similarly, if a dual-stack device had issues transitioning between dual-stack networks and IPv4 networks, we'd also know, as many phones and laptops do this all day. (E.g., my home network was dual-stack, but my work is not. Laptops — and using multiple OSes, too — moving between those networks can auto-configure themselves appropriately.) Like other posters are telling you: if you have a device that has issues when IPv6 is enabled, you have some sort of localized issue with your network setup.