With 2.83 there is now a “VOLUME” object type which can have an bpy.types.Volume data, which is a holder for OpenVDB data.
Is there a way to get the openvdb grid data via the python interface or is it expected a render engine would take the vdb filename from this and get the data itself using the openvdb api. I took a quick look but nothing obvious in python interface. Mainly a question for @brecht but relevant to other render engines I assume.