Apparently, I found the solution by randomly following an youtube tutorial on lumen.
In my project settings the “Software Raytracing Mode” was set to “Detail Tracing”. I’ve changed to “Global Tracing” and the light artifacts went away so far.
The flickering on metallic parts (frames and bedside table legs) went away after properly configuring lumen reflections on the post process volume (activating lumen reflections and setting the quality to 2). Now I’m trying to fix the shadow flickering on the wall near the wardrobe and inside the bedside lamps. Does anyone know what might influence on this? Tried increasing the distance field resolution scale on the each assets itself, but so far nothing changed.