I do not seek help of anyone but Jolla (in terms of fixing this issue). I don’t think anyone else can do it.
This forum is called Bug Reports and it is meant to report bugs. So I reported it, i.e. used this forum for what it is meant for.
It is not true that this function is not important for other users. There is another thread (and several similar older threads on TJC and TMO) where many people request the ability to block / reject unwanted calls. Such function isn’t doable with this bug present because - as I described in that thread - it also makes it impossible to hangup calls programmatically.
Completely switching the phone to silent definitely isn’t an option if one also gets important calls that cannot be missed.
Long story short, rejecting calls is the most basic phone functionality that works on ALL other existing phones and mobile operating systems. There is no sane excuse for it not working correctly on SFOS. Jolla, please fix it.