I use DraftSight.
It’s basically an AutoCad clone.
It’s as simple or as complicated as you need it to be.
It should take you no time at all to be able to produce a 2D drawing of a gasket etc.
There are loads of free online tutorials and support too.
All for free.
Paul
So far as I'm aware (but can't find the details) there is a free full version of Corel draw - an older version but older generally means simpler.
Corel can save to DXF.
Again, I can't find the details though - someone else may know what version, and what the download link is?
And again, my memory is that it's 100 percent legal / legitimate (ie a download from corel) but you would imagine if that were so, I'd be able to work it out....