Hello,
It seems ply can store vertices and also triangles not unlike OBJ format.
You can modify the header and only preserve the vertex data, then format it as a XYZ, and finally use the Lidar plugin in UE to read those data LiDAR Point Cloud Plugin Overview in Unreal Engine | Unreal Engine 5.1 Documentation
If your ply has triangle data and you want to preserve that you will have to convert it to OBJ or FBX using script you can find on the internet or free tool such as blender.