So I tried to export as .glb from UE 5.4 and the landscape seems to work but foliage is gone. There also seem to be lots of errors popping up in the GLTF/GLB importer in Blender 3.4.1
Also, I should state that the two sets of trees in the 5.3 version are one, from the material based grass system and the other is from the PCG Graph system that has been converted to static meshes. Both end up bunched together at their respective origins. (This does not happen when the foliage static meshes are exported separately using any other file type)