Datasmith generates lightmaps for objects, which is good because in Autocad I do not know if it is possible to manage several uv channels.
It seems that the generated lightmap is placed on the UV channel 2, but in the unreal object manager the lightmap index source points to channel 1 by default.
It’s a bit tedious to change the source lightmap index object by object.
This is a general concern in Datasmith import , which automatically generates lightmaps (with more or less quality), we have no choice, even when we have already created a lightmap uv channel (in max pe) we must change the index manually after import.