I was trying to add the subdivision surface to this object so I can later add a displacement modifier, but when I add it, even on Simple it creates some weird geometry bugs, can someone help?
try creating a good mesh without tris and ngons just with quads.
So, the solution is to create a new mesh with good geometry just with quads if possible. and bevel all the edges that curve when subsurf modifier is used.
If you can create the mesh its great. If not try using Booltool addon it would save lot of time in creating these kind of meshes.