The extraplanar diffuse ionised gas is a key component for understanding thefeedback processes that connect galactic discs and their halos. In this paper,we present the second study of the BETIS project, which aims to explore theionisation mechanisms of the eDIG. We use a sample of eight edge-on galaxiesobserved with MUSE and apply the methodology developed in the first paper ofthe BETIS project. We found that the vertical and radial profiles of the[NII]/Ha, [SII]/Ha, [OIII]/Hb, and [OI]/Ha ratios depict a complex ionisationstructure within galactic halos, influenced by the spatial distribution of HIIregions across the galactic plane as observed from our line of sigh, withphoton leakage from OB associations constituting the main ionisation source.Our analysis excludes low-mass, hot, and evolved stars as viable candidates forsecondary ionisation sources to elucidate the unusual behaviour of the lineratios at greater distances from the galactic midplane. In contrast, weascertain that shocks induced in the interstellar medium by star formationrelated feedback mechanisms represent a promising secondary ionisation sourceof the eDIG. We present a suite of models integrating ionisation mechanismsarising from fast shocks and photoionisation associated with star formation.When applied to the classical BPT diagrams, these models reveal that theionisation budget of the eDIG ranges from 20% to 50% across our sample, withlocal variations of up to 20% within individual galaxy halos. This correlateswith the presence of filaments and other structural components observed withingalaxy halos. The presence of shocks is additionally supported by theobservation of high-density, high [OI]/Ha ratios, characteristic ofshock-compressed ionised gas, likely induced by feedback from regions ofintense SF within the disk. These results are consistent across all galaxiesanalysed in this sample.