From InkScape to DXF
1. Save in Inkscape as PDF
Draft your design in InkScape. If there's any text, convert it to a path before or during exporting (Path → Object to Path).
Save as PDF (tested PDF v1.5).
2. Convert PDF to DXF
pstoedit -f "dxf: -ctl -mm" shape.pdf shape.dxf
Install the tool using
sudo apt install pstoedit
or
yum install pstoedit
3. Import into FreeCAD
Tested with FreeCAD 0.16.
Use the "legacy Python importer" (check this under Preferences → Import-Export → DXF).
4. Import into LibreCAD
Tested with version 2.1.2.
Use File → Import → Block and select the DXF file.