Unbend sheet metal

The part you posted in not a sheet metal part, so the unbend and flatten are not available for use for this part. The geometry is brought in from a copy geometry feature. Look at the parent model for the copy geom and if it was created as a sheet metal part you can try to flatten that model.

That part looks like it is initially bent in the "normal" manner, but then crimped or stamped to put the strengthening feature in. Does sheetmetal handle that kind of deformation? I don't know that it would...