Radio-detected populations (V-LoTSS in the left panel, LoTSS in the right panel) plotted against the canonical Güdel-Benz relationship (GBR) represented by the dashed blue line: (Williams et al. 2014), where L_X is the soft (0.1–2.4 keV) X-ray luminosity and L_v,rad is the 144 MHz total-flux radio luminosity for the LOFAR population. The radio sources without a detectable X-ray luminosity are indicated with a downward-pointing arrow and are shown as 3σ upper limits. Colours and symbols are as in Fig. 2, with the additional classification of M dwarfs beyond M4 (yellow circles) motivated by the M4 transition mentioned in Sect. 4.3.2.