When using WorldComposition and building LOD for a sublevel, textures of generated Landscape LOD are not correct when the project has forward rendering enabled.
The issue is that the material generation for the landscape LOD currently relies on the "Buffer Visualization" view mode which doesn't work in forward rendering (kinda by design).
To fix this, the material generation should be modified to rely on proper material baking like the HLOD or "Merge Actors" features. For it to work, this process would need to make a temporarily conversion of the landscape to a raw mesh (using ALandscapeProxy::ExportToRawMesh()).
(1) Open the sample project to confirm that ForwardRendering is enabled.
(2) Open "SampleLevel" under the "Sample" folder, and set the current level to "SubLevel" with the Level menu.
(3) Open "Level Details" in the Level menu, and click the "Generate" button of "LOD".
(4) Open the LOD folder created in the "Sample/Sub/" folder to confirm that the textures of generated Base Color and Normal are not correct.
(5) Uncheck the checkbox for ForwardRendering, and re-start. Then execute the steps (2) and (3).
(6) Open the LOD folder created in the "Sample/Sub/" folder to confirm that the textures of generated Base Color and Normal are correct.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-90341 in the post.