Meshes

Unreal Engine

You can export collision meshes along with your mesh. Make sure they have the same name as one of the meshes and they’re visible in the viewport.

See: https://dev.epicgames.com/documentation/unreal-engine/fbx-static-mesh-pipeline-in-unreal-engine

Blender scene with UBX prefixed collision mesh
Blender scene with UBX prefixed collision mesh

Triangulation

N-gons can be messed up when exported to Unreal. Ctrl+T to triangulate them.

Unreal didn’t seem to reimport the UVs when I tried to reimport the mesh. I had to explicitly drag the mesh from Windows Explorer into Unreal to force a reimport.

An N-gon in a UV island
An N-gon in a UV island