It’s just occurred to me that substantivalist views of space or spacetime are actually relationalist: they define location by relations between objects. It’s just that they introduce one or more additional objects—say, points or space or spacetime—to fill out the theory. An entity’s being located is then a matter of the entity standing in a certain relation to one or more of these additional objects.
Moreover, a substantivalist theory couched in terms of points may have to be even closer to relationalism, in that it may need to say that what makes the points be points of the kind of space or spacetime they are points of are their mutual spatial or spatiotemporal relations.
What has a hope of being a more radical alternative to relationalist theories are property theories, on which being in a location is a property very much like having a certain electric charge—the only difference being that the location properties have a three- or four-dimensional structure while the charge properties have a one-dimensional structure. Of course, having properties will be a matter of relation on heavy-weight Platonism and on trope theories, but these relations are not special spatial or spatiotemporal relations, but just general-purpose relations like instantiation or inherence.
Of course, maybe we don’t want an alternative to relationalism because we like relationalism.