@zimbatm I'm a sociology student and I've noticed that the more I associated websites with a high level of economic capital, the less they were likely to support IPv6.
Activist websites, with a high level of cultural capital but a low level of economic capital, tend to support IPv6. Academic ones, on the other hand, that have a rather higher global level of capital, tend not to. And websites that correspond to a capital structured by economic capital generally don't either, for example the French immigration website doesn't.
@zimbatm I'm going out on a limb here, but I'd say that you'd need both a rather low level of economic capital and rather clashing levels of economic and cultural capital to support IPv6, i.e., websites supporting IPv6 are managed by people reading significantly more, in literature and in humanities, than the average website management, but being also exposed to some level of economic scarcity, e.g. LGBTQIA+ people.
IME, the Fediverse seems to have an excellent IPv6 support.