Thank you all for your answers.
I will try the advice from @dobey when next Hybris/stable release is available. (I don't use devel channel anymore because it is not stable enough for daily use of the phone...)
Yes, your right. Our devices behaviour is very different. But you said that you hav a dual-SIM device (F8132). My device is a single-SIM device (F8131). I would think installation procedure is the same on both devices...
With the UT installation on my device it was important to do following both things before starting the UT-installer: