Usually on smaller gigs/festivals, there's either a 4x12" Marshall/Orange or a Fender Twin on the backline and I typically just plug in the cab portion of either one for my monitoring on stage. I've learned to trust that what's going to FOH is very different from what I hear and if it's accommodating for everyone else, I don't mind compromising my own stage monitoring to a certain degree as long as it sounds good out there and what's coming from my bandmates' monitor is my unaltered KPA's signal which by now I know is decent.
Bands typically follow one another during soundcheck and we are all rushed on and off stage. When I'm on, I usually just unplug the XLR from the microphone the sound crew had set up on the cabinet and plug it in one of the mains of the KPA (going mono), then have to explain to a sound guy I'm sending a direct signal (but sometimes there are language barrier/communication issues when playing in different countries). Today they had set up 2 mics on the cab (one on each speaker probably trying to go stereo?)... I did my usual routine of unplugging one and connecting the XLR to the back of the Kemper, however I found out they took the signal from the other mic (miking the twin) and not the one I was sending direct from the KPA (or mixed the 2 maybe, creating weird phase/EQ issues, god knows). I realized too late into the show what was happening and based on some people's feedback, or course it sounded a bit weird.
So today I learned my lesson; for those who are in similar situations (venue with questionable soundmen/unfamiliar with KPA) with a similar routine of sending your direct signal to FOH + cab for stage only for monitoring: make sure no sound from the cab's mic(s) can possibly reach FOH either by disconnecting any mic from the cab so they won't be tempted or make the mistake of taking the signal from the cab (unless that's what you're going for).