The #Prado embeds its objects in a knowledge graph (https://www.museodelprado.es/en/grafo-de-conocimiento/el-grafo-de-conocimiento-del-museo-del-prado) and offers RDF data for objects. However, there seems to be no way to either query the knowledge graph or download metadata for more than one item at a time.
They do have an old metadata dump on zenodo, though: https://doi.org/10.5281/zenodo.4678339
