SFR and metallicity of FRB hosts (non-repeaters shown with white-filled points, repeaters in grey), alongside the Milky Way, LMC, and SMC. The colour map shows the dependence of the XLF on SFR and metallicity on a logarithmic scaling, from low (top left, light colours) to high (bottom right, dark colours). The lines indicate XLF contours increasing in steps of a factor of 10, starting from an integrated X-ray luminosity of 10³⁹ ergs s⁻¹ for the top-left contour. The dark grey-filled point is FRB 20121102A.