The problem with Landscape has been fixed there is a commit for UE 5.4 which has been converted to UE 5.3.2
The reported fix is below
GPULM: Fix Landscape vertex factory incorrect position component format
The binary for this fix has been compiled into UnrealEditor-GPULightmass.dll
Click on the green "Code" button to get a zip which you unload
into root DRIVE:\Program Files\Epic Games\UE_5.3
This patch is currently UNTESTED, one user says it works! please test it!. Report your findings in the thread
The test file is available in the post
Remember to check DXRI is set to DX12 and SM6 in your Project setting
which are needed for all projects using EPIC GPU Lightmass (EGPU)
The SM5 shaders may need to be temporarily disabled for the projects shaders to be compiled in SM6
Recently feedback has suggested possibly turning off Lightmass Compression
to improve the quality of the Lightmass output
posting thread to report testing Landscape patch
So commit has been converted to 5.3.2 source in the file
in the path Engine\Plugins\Experimental\GPULightmass\Source\GPULightmass\Private\Scene\Scene.cpp
LEGAL
NO WARRANTY and no responsibilty on behalf of any party is given for the patch. This makes you 5.3.2 binary no longer production version
If there is a problem and you want to remove the patch.
The best way is to go into the Epic Games Launcher where you installed 5.3.2
Right click on the yellow down arrow and select "Verify".
This will remove all the patches forr Epic GPULightmass and Luoshuang’s GPULightmass patches