Radio loudness as a function of the ${\stackrel{\sim }{\alpha }}_{\mathrm{ox}}$ parameter for the objects presented in this work (blue circle, red square, and green upper limit) as well as for a complete radio-selected sample of z > 4 blazars (Caccianiga et al. 2019; Ighina et al. 2019) and z > 4 radio QSOs from the literature (Caccianiga et al. 2024, black points, and from single studies, pink symbols; see Table A.1). The shaded grey regions at ${\stackrel{\sim }{\alpha }}_{\mathrm{ox}}\sim 1.35$ and log(R)∼2 divide the parameter space in two main regions: X-ray-, radio-bright objects (top-right corner, likely blazars) and X-ray-, radio-faint objects (bottom-left corner, likely hosting mis-aligned jets, i.e., classic RL QSOs).