I just added this PR Add support for Nulls.jl based DataFrames.jl by davidanthoff · Pull Request #60 · queryverse/IterableTables.jl · GitHub that should add support for the new Nulls.jl based DataFrames.jl to IterableTables.jl (and thereby to Query.jl and all the other packages in that ecosystem).
Though note that Query.jl and the rest of the ecosystem around it will not move to the Union{T,Null} approach, but will continue to use DataValues.jl for representing missing values. The whole Union{T,Null} design has some fundamental issues that make it more or less unusable within Query.jl, as far as I can tell at this point (I’d be happy to be corrected on this point). So the situation we’ll have is that Query.jl and the iterable tables universe will be able to interop with the Nulls.jl based DataFrames.jl, but will use a different missing value story both under the hood and within any query users write.