/usr/lib/mime/packages/librecad is in librecad 2.0.2+nolibs-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 | image/vnd.dxf; libreCAD '%f'; test=test -n "$DISPLAY"; description="Drawing Exchange Format"; nametemplate=%s.dxf
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