I want to add that my issues with Lumen seem to be primarily related to the “Virtual Shadow Maps”. When I disable VSM, the performance is acceptable.
However, as the shadow quality without VSM is pretty much unusable (no soft shadows for point lights, low accuracy etc.) turning off VSM on Lumen really isn’t an option.
I guess that Lumen, in its current state, simply isn’t ready for anything beyond a directional light source and maybe a small number of additional lights.
It is perfectly okay, as it is declared as “beta” everywhere. Just wanted to add my observations here, so people who build on a similiar game environment (dungeon with many point lights etc.) don’t set expectations too high, when turning to UE5/Lumen.