Well, had a chance to get under the car and adjust the wastegate rod length.
Strange thing, but when I performed the same ISTA+ test on cold engine in the morning, it said there's no problem and link length is fine (on hot engine it said -0.52mm).
So, both the nuts were turned clockwise so the length shortened by ~0.5mm.
Also I tried to move the wastegate flap rod backwards-forwards with my hand. The flap definitely has some play around its bearing. And you know what I got? The same (or very very similar) sound that you can hear in the video above!
So now I can say for sure that's a wastegate flap.
As a result - nothing has changed (almost)
The ticking sound is still present, but I think now it's limited on 1800RPM (before it was around 2200).
Another observation (that may be wrong though, have to test it more): the sound doesn't occur new while driving on highway. The only way to replicate it is city-style driving.