I do not own any special hardware (which I believe a bus analyser would be), but I can clearly see that all the "debug" statements on the arduino side are reached and the messages are printed to the serial console. Moreover, the code on the arduino side is unchanged. As I mentioned in my very first post, I tryed it with arduino code on the ESP32 at first - and that worked totally fine. Just after switching to nanoframework on the ESP32 (but sticking to arduino code on the arduino) the read() no longer works.