Why do you want to use the monitor out? You would be better to use the main outs and send to both monitors for true stereo.
Because that was the suggestion above from another user.
Ah ok, so I can connect PC to Kemper to the "Alterantive Output" and then via the two XLR-Mainouts to my active speakers? So backing track comes from PC, my playing from the kemper and I hear both through the speakers? That was the aim of my post