I've created a form where instances and generated meshes from the Houdini HDA are combined.
I baked the HDA as actors and then converted the actors in the Outliner into packed level actors.

After baking the HDA, the mesh actors generated in Houdini come out as movable.
When building HLOD in Unreal, it seems that movable meshes are excluded. Therefore, static mesh actors need to be found and converted to static.
Even when building HLOD in the HDA state, the generated meshes are not built.

Need to specify a specific attribute values?

Houdini 20, unreal 5.3

HDAs can adjust the unreal actor properties by using uproperties attribute. In an attribute wrangle, set to points, apply

`@unreal_uproperty_Mobility = 0;`

This will switch bake mobility to Static. 1 Will do Stationary. 2 will be Moveable.