Hello Heinz, all,
first of all thank you for sharing your work in this thread!
I have not to much skills around programming and arduino, but was however able to build this and integrate my Vallox 90 SE into ioBroker. Absolutely Great!
You mentioned the bypass damper above and I see you have visualized it in fhem. I found the Value to set the Threshold temp for this (31), however I wonder where you got the actual bypass position from. Which Value shows if its open or closed?
I do not want to control it, i just would like to log the Position Status to see when it happens.

Thanks a lot i feel blind :)