As @HolyBlackCat pointed out, using a class with specializations and a static member function (and using a separate function as a nicer interface to the specializations) solves the problem. The class specialization for ranges now looks like this:

template <sink_c sink_t, std::ranges::sized_range value_t>
requires requires(sink_t& sink, std::ranges::range_value_t<value_t> element) {
    { DefaultWrite<sink_t, std::ranges::range_value_t<value_t>>::call(sink, element) };
}
struct DefaultWrite<sink_t, value_t> {
    static void call(sink_t& sink, value_t const& value);
};