A workaround, not a solution is to place a postprocess volume and only on this room to change the reflection type to hardware deprecated and put 4-5 reflection bounces. Lumen mirror reflections are not there yet.
I add a “Rec Light “
Desactive “Cast Shadows”
Light Amount “ 0.15 candles”
The light need to point to the wall in front on the mirror - And need to be near of the wall. The issue is :indirection light is not enough to illuminate the area.