Hi !
Interesting.
a) I designed a simple plane in Blender as a flag. (No bones attached).
b) Exported it as an fbx-file.
c) Imported it into EU 4.18 as a skeleton mesh.
d) Used Cloth tool to select area, set up clothing data, applied etc etc.
e) Placed it in the scene and applied wind. WORK VERY WELL.
But it does not collide properly at all with other objects, ie static mesh (for ex a stone-wall)
BR Jörgen Petersson in Sweden.