hi @Unreal_ArchViz @KaraevElmin1 @ATNeo
ln the LGPU lightmass rect lights (Rectangular Area Light) unfinished:
only that kind of light is not baking any Global Illumination indirect lighting, only direct one.
This means you will use CPU for Rect Lights.
from documentation
The following lights settings are not yet supported with GPULM:
Indirect Lighting Intensity
Source Texture (with exception of Rect Lights)
Some of these settings can be used partially with Stationary lights. The baked GI will not honor the feature, but the dynamic direct lighting from the light source will.
There are many settings to tweak the results of lightmass for the CPU-based workflow. Most of these settings are not used with GPULM and do not have equivalent features or settings.
There is possible workaround. You have to make a surface with the same dimensions of the Rect Light, with an Emissive material attached
Using the Emissive Material Input | Unreal Engine Documentation
All lights are described in
Light Types and Their Mobility in Unreal Engine | Unreal Engine 5.2 Documentation.