V2.4 (V2 plus4) is still two port one path, but overall architecture is redesigned and port 2 return loss is much improved (typically >20dB) so you can get good results reversing the DUT and using two port one path calibration:
ttps://scikit-rf.readthedocs.io/en/latest/api/calibration/generated/skrf.calibration.calibration.TwoPortOnePath.html
OwO