Revisiting Buchdahl transformations: new static and rotating black holes in vacuum, double copy, and hairy extensionsJosé Barrientos, Adolfo Cisterna, Mokhtar Hassaine and Julio OlivaEur. Phys. J. C, 84 10 (2024) 1011DOI: https://doi.org/10.1140/epjc/s10052-024-13383-4