The only program that can reliably produce .fcstd files is FreeCAD from which this particular CAD drawing format originates. So if you are hoping in a conversion of DXF 2D CAD files to FCSTD format, you have to use FreeCAD. No other software can help you.
Convert AutoCAD DXF Drawing Exchange Format to FreeCAD drawing.
We found one software available in the database for this conversion.
Multiplatform software - convert dxf to fcstd on any platform
An open source multiplatform 3D CAD/MCAD/CAx/CAE/PLM modeler
Convert from dxf file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.