Posterior distribution of the source parameters disfavoured values for the Varying A_r scenario. The corresponding models are disfavoured by the LOFAR upper limits from Mertens et al. (2025) at z = 9.1. Red refers to the case when each redshift is considered separately (Single-z) at z = 9.1, while blue represents the joint MCMC analysis results (Joint-z). The contour levels in the two-dimensional contour plots refer to the 1σ and 2σ credible intervals of the disfavoured models. The diagonal panels represent the corresponding marginalised probability distributions of each parameter.