Remarks on propagating waves in non-linear vacuum electrodynamics M. A. Pérez-García, A. Pérez Martínez and E. Rodríguez Querts Eur. Phys. J. C, 83 8 (2023) 746 Published online: 22 August 2023 DOI: 10.1140/epjc/s10052-023-11902-3