Okay, in the simulator images could be solved, but this does not help at all! Using a real sky and real devices I still have problems. Yesterday night it took me 3 hours to test several things. I tried running KStars directly on the RPI4 and I tried KStars connected remotely to the RPI4 and detected a lot of new issues and finally capture & solve did still not work.
When I'm trying to capture & solve using my Canon EOS 700D it always fails - on the RPI4 and also via remote connection. And as I mentioned earlier, I can not see any star inside the image shown during capture and solve!!!!