Yesterday I test the FreeCAD defeaturing (on v0.22.1) and… it just works! Amazing. I was able to delete simple features as holes, faces, radius and chamfers. It will not solve complex situations or fix wrong file conversions, but what he do, it does well. I miss a simple way to move faces still, or just delete one or two conflictive surfaces and replace with a simple surface patch.
There was an external tool in FreeCAD to do defeaturing, but is far more complex and didn´t solve some situations that this tool do.
If you want to try, just impor your stp file in the Part workbench, select the faces that you want to delete, and go to Menu/Part/Defeaturing… and that its! Magick!
@Matej , I was reading in the link, that the Defeaturing is part of the OpenCasacade CAD kernel, is the same in use in PrePoMax? Maybe could be included then this feature, is very usefull and could be a killer feature.